Avengers: Infinity War effectively changed what could be done in an MCU movie. Willing to off popular characters, directly fight against progression in previous films, and have the villain as its protagonist, it was a drastic change from what fans of the franchise were used to. Likewise, it's clear that the resolution to Thanos's snap in Avengers 4 won't come without its own fair share of changes for the MCU in the future. Stopping the Mad Titan and the effect of the Infinity Gauntlet will likely require some big sacrifices. It will be the largest conflict the Avengers have ever faced, and it will probably have some lasting effects that bleed into Phase Four, if not directly causing its events. After all, the events of Captain America: Civil War were felt in several movies, including Ant-Man and the Wasp, Spider-Man: Homecoming, and Black Panther. On all accounts, Avengers 4 should have a similar effect.
After Thanos used the Gauntlet to rid the universe of half of all life, many have wondered how the Avengers will rectify this tragedy going forward. Many fans have taken to the internet to post their theories about how Avengers 4 could end, how Earth's Mightiest Heroes defeat Thanos once and for all, and how that conflict will change the MCU going forward. A lot of the theories we've seen are quite plausible and open the MCU up for new and exciting conflicts in Phase Four and beyond. Prepare to think about the future of the MCU as we go through 20 bonkers fan theories about the ending of Avengers 4.
20 SKRULLS ON THE RISE
The Skrulls are finally making their live-action debut in Captain Marvel, and many people have suggested that it won't be the last time we see them on-screen. It would be easy for a post-credits scene in the film to confirm that the Skrulls were on Earth and had taken the identity of a character we recognize.
Some have speculated that the events in Avengers 4 could seemingly reveal who the Skrull is, if not subtly introducing them to the modern MCU, setting them up to be the villains of Phase Four. Imagine a post-credit scene where someone like Falcon or War Machine is revealed to have been a Skrull all that time...
19 CREATION OF MUTANTS
With Disney finally bringing FOX under their belt, they now have the rights to the X-Men and mutants of the Marvel Universe. While it's clear they weren't going to be shoved into the MCU as early as possible, they could be integrated with its future plans.
Some fans suggest that the mutant gene could be something only able to be activated following exposure to an Infinity Stone, thus explaining how we can still have Scarlet Witch and Quicksilver without the rest of the mutants. After everyone comes back from the snap, tons of mutants will be revealed across the world in some sort of post-credit scene, paving the way for the X-Men.
18 INTRODUCTION OF THE MULTIVERSE
We already know there are multiple dimensions that exist in the MCU. The Mirror Dimension, Dark Dimension, and Quantum Realm are all different realities that exist within the MCU. However, we have yet to see any confirmation of the Multiverse as it exists in the comics, with alternate realities that have different versions of the characters we recognize.
Some fans speculate that the Avengers could get Infinity Stones from one of these alternate realities to construct their own Infinity Gauntlet and stop Thanosm which could also open the door for some crazy MCU movies in the future.
17 CAPTAIN MARVEL DEFEATS THANOS
When Nick Fury saw himself and just about everyone in the world turning into dust, he thought of only one thing to do: call Captain Marvel. It's clear that there's something about this hero that puts her on a much different level than the rest of the Avengers -- Kevin Feige has already confirmed that she's the strongest superhero in the MCU.
This leads many fans to believe that she'll be the one to defeat Thanos. If the Avengers create their own Infinity Gauntlet, it's possible that she's the one who would hold it and bring an end to the Mad Titan's new world.
16 THE LIVING TRIBUNAL INTERVENES
The Living Tribunal is a massive entity in Marvel Comics that serves as the overseer for the universe as the characters know it. Its purpose is to maintain balance and prevent its destruction. While the Tribunal has yet to make its appearance in the MCU, it's possible that Thanos's effect on reality could spur it to finally reveal itself.
There were some rumors that Doctor Strange had a scene in which he was against an entirely CGI character that was extremely expensive to create. It's possible that Strange could communicate with the Living Tribunal as a means of trying to save the universe.
15 NOVA JOINS THE FINAL BATTLE
With Thanos having annihilated Xandar by the start of Avengers: Infinity War, some have speculated that it could serve as the origin story for the hero, Nova. As the last survivor of his people, he could have the powers necessary to become a hero of his own. If that's the case, it's quite possible that he could arrive in Avengers 4 and even join the Avengers during the final battle against the Mad Titan, seeking revenge for his home planet.
If he doesn't show up in Avengers 4, we may get a post-credits scene where he is teased for Phase Four. Either way, Marvel has the perfect opportunity to introduce him.
14 CAPTAIN AMERICA'S LAST STAND
Captain America, much like Iron Man, has developed throughout the history of the MCU. After leaving the Avengers in Captain America: Civil War and returning to fight Thanos in Avengers: Infinity War, this nomad now has the time to return to his mantle of Captain America. In Avengers 4, it's all but confirmed that the Avengers will reunite.
With him leading the Avengers once more and completing his arc, it would be a fitting end to his character. After all, he had a powerful speech to Thanos in the comics before meeting his end, and many speculate that he could lose his life in Avengers 4 in a similar way.
13 HULK AND THANOS REMATCH
After Hulk has essentially dominated his way through the MCU, he got knocked down a few pegs at the start of Avengers: Infinity War. He fought the Mad Titan in a one-on-one match on the Asgardian ship and lost, much to his dismay. After refusing to come out for the remainder of the film, it's likely that Hulk will return in Avengers 4 with a new outlook on life.
Making his return, some theorize that it will also bring about a rematch between the Hulk and Thanos, with the Hulk coming out on top this time around. Perhaps Hulk and Banner will have finally connected with each other and be fighting as one.
12 TRADING LIVES
Many fans have pointed out that it wasn't coincidence that caused all of the original Avengers to survive the snap. In Avengers 4, Cap, Iron Man, Black Widow, Hawkeye, Thor, and Hulk will likely have big roles to play in the film. Their big task will be to bring back all of the other heroes who turned into ash, leading some fans to think that there may be an element of sacrifice involved.
In order to save the MCU heroes, they may have to give up their own lives in the process, which would resolve the issue of actors' contracts as well as make Avengers 4 a passing of the torch in many ways.
11 PARTS OF THE UNIVERSE GET DESTROYED
If there's anything we've learned from the events of Doctor Strange, it's that messing with time and the universe as a whole comes with serious consequences. Thanos has already manipulated time, and if the Avengers have to use time travel themselves in Avengers 4, then it's possible that the universe will take a severe hit.
With Xandar already on the outs, some fans have theorized that we could see more familiar planets get destroyed, like Sakaar from Thor: Ragnarok. These planets being destroyed could also be a direct result of Thanos using the Infinity Gauntlet, which is but one problem the Avengers have to handle.
10 BUCKY BECOMES THE NEW CAP
Captain America seems like a character that will meet his end in Avengers 4. One way or the other, Chris Evans is done with the MCU after the movie, leading some to speculate that he might pass the torch down to someone else. When talking about who could be the next Captain America, most fans believe that Bucky is the most deserving.
He was always Steve's last tie to his old life and knows him better than anyone else in the world. Sam Wilson would be a decent choice, but most feel that Bucky is much more deserving. After all, Bucky was with him til the end of the line.
9 REBIRTH OF ASGARD ON EARTH
At the end of Thor: Ragnarok, Thor was taking the remaining Asgardians to try and rebuild the nation in Norway on Earth. However, he was stopped along the way by Thanos, who directly offed around half of those who were left.
It's possible that, once his crusade to find the Mad Titan and end him is over, Thor might look for Valkyrie, Korg, and the rest of the Asgardians. While the resulting nation would be small, he could easily began rebuilding Asgard on Earth at the end of the movie, giving the God of Thunder a taste of hope for once in his life.
8 USING THE QUANTUM REALM
Ant-Man and the Wasp did little to comfort us after the end of Avengers: Infinity War, but it did show us one thing: the Quantum Realm is a possible defense against the effects of the Infinity Gauntlet. With Scott Lang knowing all there is to know about the Quantum Realm, his appearance in Avengers 4 may come with a few ideas on how to defeat the Mad Titan.
With the Avengers desperate and in need of a new plan, it's likely that they will use the Quantum Realm to try and either revive their friends or even travel through time (with the mention of a Time Vortex). One thing is for sure: Marvel wouldn't be setting up the Quantum Realm if there wasn't a larger purpose.
7 THE NEW GUARDIANS OF THE GALAXY
Gamora already met her end in Avengers: Infinity War and whether she'll return in Avengers 4 or not is anyone's guess. Guardians of the Galaxy Vol. 3 was in the books for Marvel, but after James Gunn got fired, things were a bit different.
It's possible that Disney could use the opportunity to have a new Guardians team or at least "clean up house" a little bit and create an entirely new team. Some fans think that Drax could perish in Avengers 4 and that Gamora won't be brought back. Others think that Mantis will also lose her life and the Guardians will look for a way to bring Gamora back in their next outing.
6 HULK WITH THE INFINITY GAUNTLET
Hulk will likely be going through a big change in Avengers 4. After Thor: Ragnarok saw the Hulk in control and Avengers: Infinity War saw Bruce Banner in control, Avengers 4 will likely be the completion of their arc, possibly having the two come together to form Professor Hulk.
This more balanced version of the Hulk could possibly be the one to wield the Infinity Gauntlet, according to some fans. With a newfound intelligence and a much more manageable temper, he could be the one to defeat the Mad Titan. After all, there's no doubt that he'd want some payback on Thanos.
5 THANOS SURVIVES
Most people expect Thanos to lose his life in Avengers 4. With such a big threat in the cosmos, it seems like the Avengers won't feel that the job is done unless they defeat him. Marvel can't pull a "Thanos as a farmer" scene either, because that's essentially how they ended Avengers: Infinity War.
Some fans have brought to the table that the Mad Titan could survive the film, though, to appear as a supporting character in other films. For example, Marvel still has that Eternals film in the books, and Thanos would be a good fit for that movie, considering his heritage is directly tied to them.
4 THE BEGINNING OF THE ILLUMINATI
The Illuminati in the comics were a group of Marvel superheroes who were tasked with making the big decisions for the fate of the Earth. Each one of them was also responsible for guarding the Infinity Stones, and at the end of Avengers 4, it's clear that the world will never be the same.
With characters like Black Panther, Doctor Strange, and (possibly) Iron Man still on the table, some fans believe it's likely that the end of the film could see the beginning of the Illuminati. While the roster could look a bit different depending on who lives and who doesn't, it seems like a natural progression after such a cataclysmic film.
3 CAPTAIN MARVEL AS THE NEW AVENGERS LEADER
Iron Man and Captain America have served as the leaders of the Avengers, respectively. However, it's all but confirmed that, one way or another, the two of them will no longer be a big part of the MCU following Avengers 4. That said, Earth's Mightiest Heroes will still need someone to lead them when threats get too big.
The best candidate, as many theorize, is Captain Marvel. Not only would that bring a new dynamic to the Avengers, but it also would go along with how Kevin Feige described her as the new face of the MCU. What better way to make her a popular character than by having her take over for Stark and Rogers?
2 THE END OF IRON MAN
This is one of the most popular theories out there. Tony Stark started the MCU and since then, he's been its biggest hero, nearly sacrificing himself in The Avengers and then leading the charge against Thanos in Avengers: Infinity War. Because of all the work he's done in the world, many speculate that it's his time to finally bow out of the franchise.
With many of his friends gone and the disappearance of Peter Parker in his arms, Tony will likely have a renewed drive to taking down Thanos and saving the world. This time, it may require an intense sacrifice -- one that he will be more than willing to take.
1 THANOS SEES THE ERROR IN HIS WAYS
A lot of people have stated that Thanos having some sort of epiphany and helping the Avengers restore balance to the universe would be a cheap trick based on the stakes set up in Avengers: Infinity War. That said, it's something that many fans believe we could see a version of in the film.
One potential route is that Gamora speaks to Thanos through the Soul Stone and he starts to have second thoughts, which cause him to hold back in battle and be defeated by the Avengers. Another route is that he begins to regret "balancing" the universe and finds the Avengers to try and fix the problems he caused.