With Avengers: Endgame, Tony Stark died, Captain America got old and Thor headed into the cosmos with the Guardians of the Galaxy. All of these events made room within the Marvel Cinematic Universe to explore entirely different stories in Phase Four and gave some familiar characters with space for their perspectives to be told.
The upcoming film and streaming slate Marvel Studios announced at Comic-Con International in San Diego demonstrates an eagerness to embrace new stories with diverse casts and push into new genres like horror. While Spider-Man: Far From Home, already started to chart the post-Endgame MCU, Marvel's current and expected film slate could hint at a few big crossovers that could already be in the works.
One of Far From Home's biggest twists came in the post-credits sequence when it was revealed that Nick Fury and Maria Hill were Skrulls. They were Talos and his wife, Soren, masquerading on Earth while Fury was off-planet on some sort of galactic vessel. This means there might be even more Skrulls on Earth, setting the stage for a potential Secret Invasion event.
While Talos' people might be friendly, since Fury and Captain Marvel were their allies, we don't know if other Skrulls are friendly or hiding on Earth, possibly looking to conquer the planet for themselves after the Kree Empire destroyed their homeworld. Talos did mention that Kree sleeper cells still existed, so Earth might be the stage for a next intergalactic war come Captain Marvel 2, which Marvel Studios president Kevin Feige admitted is coming. With these shape-shifters hiding in plain sight, we have no clue what positions of power they might occupy to help them possibly take over the world, but it's clear that Marvel's heroes probably won't see it coming.
HOUSE OF M
In the comic book Marvel Universe, House of M occurred when Scarlet Witch created an alternate reality to safeguard the mutants she loved. She was tricked into it by Quicksilver, but the MCU could flip the script to evolve Wanda Maximoff beyond just telekinetic and psychic powers. For some time, her reality-bending abilities have been rumored to be her next evolution, and this may happen in the Disney+ WandaVision series.
What's all the more intriguing is Wanda might even rip a hole open to the Multiverse, since she's going to appear in Doctor Strange in the Madness of the Multiverse. Strange could find himself hurtling though other realms and alternate dimensions, with Wanda's actions somehow tying in. It stands to reason that she might have created some doorways herself, which could even include a utopia with Vision and her kids or even a world closer to the House of M comics, thus giving mutants an entrance to the MCU.
One of Marvel's best modern cosmic stories is the 2006 Annihilation event, which dealt with Annihilus and the Annihilation Wave spreading through Marvel's cosmos. It brought Marvel's galactic heroes and the Nova Corps together as a resistance, and even the likes of Galactus, the Silver Surfer, the Kree and the Super-Skrull were dragged into conflict. This has potential to be an epic on the scale of Endgame, and with Thor and the Guardians out in space, the MCU already has heavy-hitters awaiting such a foe.
Apart from reinvigorating the Corps and giving other cosmic characters an entry point, Annihilus as a threat is ideal way to introduce the Fantastic Four. Having them picking up on this incoming disaster on Earth or while exploring the Negative Zone really would create a fairly natural way to bring Marvel's first family into the MCU in a major way.
Secret Wars offers two opportunities for the MCU to place an ensemble of heroes and villains at each other's throats. If the MCU follows the '80s storyline, we could get the Beyonder pitting these figures against each other to see who really deserves top spot in his Battleworld. Various Avengers, mutants and villains all appeared in it, and it would definitely be the ultimate battle royale. In the wake of Thanos' defeat, this feels like the kind of esoteric high-stakes storyline that could happen when cosmic gods like the Beyonder decide to intervene.
However, 2015's Secret Wars, also offers a few enticing options. That story revolves around God Emperor Doom and the death of various worlds in the Marvel Multiverse. Doom needs a grand entrance himself, and having him seeking out what remains of the Infinity Stones to remodel reality is quite an entertaining thought. This also would link Avengers, the Fantastic Four, Black Panther and the Illuminati, and other villains together in another epic story. If the studio chooses, it can even be condensed for a more intimate adventure with a smaller cast on Doom's new "Battleworld" that could make a way to bring Miles Morales or other Ultimate Universe characters a role in the MCU.