The first phase of Marvel Cinematic Universe movies culminated in the release of 2012's The Avengers, solidifying the team as central to that universe. Phase 3 has just ended, with its penultimate chapter being Avengers: Endgame. Given the impact the team has had on the MCU, many were shocked by its absence from Marvel Studios' slate revealed at Comic-Con International in San Diego. As strange as this may seem to longtime fans, there are several very good reasons for this.
Conclusions and New Beginnings
Avengers: Endgame was all about just that: conclusions. Over ten years of character development and stories were brought to varying levels of closure with the film, and the stories of several major Avengers ended, notably Tony Stark/Iron Man, Steve Rogers/Captain America and Natasha Romanoff/Black Widow. Marvel Studios President Kevin Feige himself remarked at not wanting to have another Avengers movie so soon after Endgame in order to focus on new and existing characters.
As many of the old characters from the "Infinity Saga" are gone or have had their status quos irrevocably changed, Phases 4 and 5 will introduce a number of new characters, including Shang Chi, The Eternals and even Blade. These characters will explore new territory, with the Shang-Chi and Eternals movies being some of the first mainstream appearances of those characters outside of the comics. It would be a lot harder for fans to get excited about these new concepts if Marvel was still forcing the universe to revolve around Earth's Mightiest Heroes. Big concepts like The Eternals would especially be robbed if they were used as stepping stones to set up the next Avengers crossover movie event. By allowing new narrative zones to be entered, Marvel can branch out, making its inevitable return to an Avengers or similar ensemble movie stronger.
Announcing another Avengers film so soon could have some pretty negative effects. For one, it might cheapen the events of Endgame, which really shook up the universe and it characters. Reuniting the team so soon would undermine just how torn apart it was at the end of that film. Secondly, Marvel Studios needs to make clear it can reassemble a team made up of new, interesting and lovable characters, and that means giving audiences time to get to know the next generation of Earth's Mightiest Heroes.
What Could the Next Team Look Like?
Avengers founders such as Thor, Hawkeye and Hulk are still out there, and it's totally possible they'll play a role in the coming action. Thor is the sole Avenger to get a solo movie in Phase 4, and he may appear in the third Guardians of the Galaxy film. Hawkeye will get his own Disney+ show, which will feature Kate Bishop, potentially setting up his replacement. Hulk is a slightly different story, as the injury he sustained using the Infinity Gauntlet may, in fact, be permanent.
There are also Scarlet Witch and The Vision. Despite the latter having died, the two are set to get their own TV series on Disney+, so there's a good chance they've still got some role to play in what happens in the MCU. Spider-Man is also a recognizable character who's still swinging around, so he could potentially join a new Avengers team. The same goes for Captain Marvel and Black Panther. Using these characters in future projects will help give existing fans entry points into learning and loving new characters.
The Young Avengers may also play a role in the MCU post-Endgame, and waiting at least a few years to make this film would be for the best. The most effective way to make that new team felt is to establish its characters first, which will definitely take a few years. Both the real and cinematic worlds would need to miss Earth's Mightiest Heroes before replacing them. By allowing viewers to see several movies (and possibly several phases) without the Avengers anywhere in sight, Marvel would ensure the next Avengers movie is an event. It would also be a good way to further showcase the more diverse path that Marvel seems to be following from here on out.
There are also the characters Disney acquired from Fox, chief among them being the Fantastic Four and the X-Men. Marvel's mutants may be pushed to become the new focal team of the MCU, or they may share that role with the Fantastic Four. Feige did tease Marvel Studios' plans for both teams, so they're likely to make their way to the MCU sooner rather than later, and with them comes a whole new world of possibilities.