Marvel Studios seemingly pulled off the impossible. When the third phase of the Marvel Cinematic Universe comes to a close, Marvel will have released 22 movies that all connect to tell a larger story arc. The studio will have spent a decade pulling off one of the most complex, and successful, cinematic feats in movie history. Of course, things aren't going to end with Avengers 4 (2019). In fact, studio head Kevin Feige has stated that the studio already has plans for another 20 movies.
In order to prevent spoilers for Infinity War (2018), Marvel has been very tight lipped about their plans for Phase 4. Even though details are scarce, fans can still figure certain things out. The Guardians of the Galaxy, Spider-Man, Dr. Strange and Black Panther are all expected to return. The real question is: what will happen in Phase 5. It's likely that Phase 4 will mostly deal with setting up the MCU past Infinity War, the same way Phase 1 set up the eventual clash with Thanos. The next epic chapter in the MCU is likely going to be Phase 5, and nothing is known for certain. That hasn't stopped fans from speculating, though! Here are the juiciest rumors we've heard (so far).
15 THE X-MEN DEBUT
When it was announced that Disney had reached a deal to purchase 21st Century Fox, fans immediately began expecting the mutants to show up in the next MCU movie. Unfortunately, the deal is fairly complicated and is going to take over a year to finalize. So, as anxious as everyone is, they're going to have to wait. Most likely, we're all going to be waiting a long time.
Marvel most likely already has Phase 4 planned out, and is just holding off on making announcements to avoid spoiling Phase 3. Unlike Spider-Man, who only required minor shuffling to insert into Phase 3, the X-Men franchise is huge. Marvel has multiple films to figure out, and it's likely too overwhelming to fit into a pre-existing plan. It's rumored that hints and cameos for the X-Men may begin in Phase 4, but the mutants won't make their debut until Phase 5.
14 DOCTOR DOOM WILL BE THE MAIN BAD GUY
Thanos will most likely be defeated by the end of Phase 3. That leaves a very large "villain shaped" hole in the MCU. A big reason why Thanos' fight with the Avengers is so anticipated is because Marvel spent years building him up as a threat. It's been speculated that Phase 4 will try to repeat this formula, and only start dropping hints as what the next major threat the Avengers will face.
Once again, Phase 5 is likely the earliest that Marvel will be able to fully take advantage of the X-Men and Fantastic Four franchises. This includes Doctor Doom, arguably Marvel's best villain. In order to do him justice, Marvel needs to take the time to set him up. It's possible that Dr Doom is only hinted at in Phase 4, in order to have his machinations be the focus of Phase 5.
13 NO MORE SPIDER-MAN
Marvel scored a major victory by working out a deal with Sony to include Spider-Man in its cinematic universe. Sony still owns the film rights to Spider-Man, but is allowing the character to appear in Marvel movies, as well as letting Marvel produce Spider-Man movies. The stand-alone films still fall under the Sony banner, however. Homecoming (2017) was a hit, and successfully relaunched the wall crawler's film career.
Sony obviously noticed this, and plans on releasing Venom in 2018. This film is part of the Spider-Man universe, but not necessarily the Marvel Universe. It's likely that Marvel isn't thrilled about Sony expanding the Spider-Man cinematic universe in ways that don't involve them. If this is the case, don't expect the deal to be extended, leaving Spider-Man out of Phase 5.
12 DEADPOOL CONTINUES
Just like with Spider-Man, it's more than likely that Marvel will reboot X-Men for the MCU. That means that everything that's happened since X-Men (2000) onward will be wiped clean. Marvel will be able to do what it wants with the characters without being beholden to any of the previous continuity. Then there's Wade Wilson.
Deadpool (2016) was a surprise hit, and the sequel is building a substantial amount of buzz around it. The merc with a mouth might be too popular to just get rid of. Also, being rated R, Deadpool might work best existing alongside the MCU. If Phase 5 includes Deadpool, it's rumored that it will be the current Ryan Reynolds version and not a new, Disney-fied version. It's also likely that Deadpool films will continue to be produced, but exist outside or alongside the MCU.
11 A FRESH START
By the time Phase 5 comes around, the MCU will be around 16 years old. By that point, Marvel is going to have to let go of at least some of its actors. The studio's been doing a good job of introducing new characters, but it has also relied on a core group of characters to hold down its line-ups.
Even Marvel's newer properties are going to be getting older by Phase 5. Doctor Strange (2016) will be seven years old by the time Phase 5 is likely to start. This means that for the first time, Marvel is unlikely to have any of its original heavy hitters to rely on. It's believed that the focus for Phase 5 will be introducing the next class of Marvel franchises. It will be the first phase that doesn't look similar to the first.
10 NEW FACES, FAMILIAR MASKS
Of course, the more popular rumor is that Marvel is going to continue on with the same franchises, and just change the secret identities. Chris Evans can't play Steve Rogers forever, but that doesn't mean that someone else can't be Captain America. The popular theory is that one of the supporting characters, like Sam Wilson or Bucky, would take up the mantle. The problem with that is obviously that both of those actors will also be getting older and looking to move on or retire.
Many believe that Marvel will introduce new, younger actors for future films. Many also believe that they won't debut as the new Cap (or Iron Man, or Thor, etc) until Phase 5. Marvel might introduce the new character in Phase 4, and let fans get used to them first before having them take on a cherished identity.
9 FULL REBOOT
Phase 5 might not actually be Phase 5, but instead Phase 1.2 (or something along those lines). When looking to the future, Marvel might decide to stick with what works. Realistically speaking, the MCU can only go on with the same continuity for so long. As time passes in the real world, time has to pass in the MCU. At some point, the continuity of a 30 film franchise might become too big of a burden. Frankly, there are a lot of reasons Marvel might consider a full on reboot and start from scratch.
This would allow Marvel to keep using its most popular characters, while also skipping the mistakes it previously made. In the year 2000, Marvel launched the Ultimate Universe of comics, which was a modernized take on the classic universe. It's possible that Phase 5 might be an Ultimate version of the MCU.
8 NOVA
The Nova Corps exists in the MCU. It first appeared in Guardians of the Galaxy (2014), where they served as a police force for parts of the universe. In the comics, the most notable Nova Corps member is Richard Rider. He first appeared in Nova #1 (1976) by Marv Wolfman and John Buscema, and eventually went on to become the last remaining Nova. As Nova Prime, he helped Star-Lord bring together the current version of the Guardians of the Galaxy.
To be honest, it's a little weird that he hasn't appeared in the films yet. It seems like the only reason why he hasn't is because James Gunn, director of Guardians of the Galaxy, doesn't want to include him. Since Gunn is returning for another Guardians entry in Phase 4, it seems like Nova's earliest chance to appear is Phase 5.
7 ANNIHILATION
Marvel's going to have trouble following up Infinity War (2018) and whatever the plot of Avengers 4 (2019) ends up being. Based on The Infinity Gauntlet (1991) by Jim Starlin, George Perez and Ron Lim, it's the culmination of a decade's worth of storytelling. While Marvel has plenty of comic book storylines to draw inspiration from for years to come, none have the same scope as Thanos' quest for the Infinity Stones.
That is, except for Annihilation (2005) by Keith Giffen. The comic saw the entire universe put at risk when Annihilus unleashes the Annihilation Wave from the Negative Zone. The series led to the current version of The Guardians of the Galaxy, so it's likely film fans would embrace it. Once again, Phase 4 has to deal with the fallout from Phase 3, so a story of this scope would have to wait until Phase 5.
6 SUPERNATURAL HEROES
The current MCU seems to be dominated by Marvel mainstays and its cosmic characters and villains. The franchise has mostly decided to rely of science fiction themed heroes. The only supernatural character is Dr. Strange, and even some of his powers are tied to one of the infinity stones. This makes sense, but the MCU is missing out on a wide array of Marvel characters.
Marvel has a rich roster of supernatural characters, most notably Ghost Rider. He definitely belongs in the MCU proper, instead of just being relegated to the TV side of the MCU. Given that he recently appeared in Agents of S.H.I.E.L.D. (2013), Marvel's probably going to want to wait before introducing a film version. Fans aren't expecting Marvel to start exploring the supernatural world until Phase 5, keeping enough distance between the TV appearances and the film entries.
5 SECRET INVASION
Fans were surprised when it was announced that Captain Marvel (2019) would feature the Skrulls as the villains. They are an alien race of shapeshifters that first appeared in Fantastic Four #2 (1962) by Stan Lee and Jack Kirby. Many assumed that this meant that Fox owned the film rights to the aliens, since it owns the Fantastic Four rights. It turns out, Fox only has the rights to specific characters, but the race is co-owned.
Interestingly, Captain Marvel is going to be set during the '90s. It's been rumored that this might set up Secret Invasion (2008) by Brian Michael Bendis. Captain Marvel would introduce the race, and then Phase 4 would end with it being revealed that the Skrulls have infiltrated the MCU. Phase 5 would then deal with the ramifications and eventual battle.
4 TV HEROES ON THE BIG SCREEN
The MCU doesn't just exist in the movies. There's also a connected line of tv shows, including Agents of S.H.I.E.L.D. (2014) and the Netflix Defenders line up. Initially, the TV shows followed the events of the films, with the plots of Thor: The Dark World (2013) and Captain America: The Winter Soldier (2014) having ramifications on Agents of S.H.I.E.L.D. Over time, however, it became too complicated to coordinate and the TV shows, Netflix series and movies don't have much impact on each other.
Even more surprising, characters don't cross over from TV to movie. Reportedly, it's just too complicated to coordinate and make sure everything makes sense. It's also possible that Marvel is holding off on having the Defenders appear in the films until a huge, Phase 5 ultimate team-up movie just to keep fans in anticipation.
3 MULTIPLE UNIVERSE
Doctor Strange (2016) introduced the concept of multiple realities to the MCU. In the comics, there are countless alternate realities, creating a vast multiverse. Some of Marvel's most successful stories have been centered around alternate realities. There's Age of Apocalypse (1995), Marvel Zombies (2005) and the entire line of What If…? comics.
It's likely that Phase 4 will explore some of these universes, but Phase 5 might take things even further. Instead of having one MCU, entire movies might be built around alternate universes. Considering that by Phase 5, it's likely Marvel will have the X-Men rights, this makes sense. Logan (2017) proved that fans care about these characters enough to see a movie that doesn't fit perfectly into continuity, and Marvel would be smart to further explore concepts like this.
2 SECRET WARS
Back in 1984, Marvel unleashed Secret Wars by Jim Shooter and Mike Zeck. It was one of Marvel's first huge crossover events, combining all of their most popular characters into one, massive story. A seemingly omnipotent entity calling itself the Beyonder gathers a group of heroes and villains and transports them to a place called Battleworld. Here, the two sides have to fight it out in order to win whatever they desire.
Clearly, Marvel Studios draws inspiration from classic comics. Secret Wars is one of the most famous Marvel crossovers, so it's likely that it's at least been discussed. It's too big of a story to rush into Phase 4, but many fans believe (or at least, hope) that it'll be the story arc for Phase 5.
1 MARVEL VS DC
At first glance, this seems impossible. There's no way that the MCU would ever crossover with the DCEU. They're rivals, and with Marvel easily in the lead, why would they help out the competition? Fans may dream of it, but the odds of it becoming a reality are slim to none. Of course, that's what many said about Marvel Studios pulling off The Avengers (2012) and the rest of the MCU.
In all honesty, by the time Phase 5 comes around, it's going to be hard to get fans excited. Marvel's going to be running out of characters, and audiences are getting used to seeing them team up to save the world. By Phase 5, the only surprise left would be Marvel vs DC, and Marvel Studios is all about pulling off the impossible.