Marvel's Avengers will finally allow players to pick the same hero in the same mission, but only as part of a special event.
The Tachyon Anomaly event is set to begin some time this spring, according to the newly published Avengers 2021 Content Roadmap. On top of letting teammates play as any combination of heroes - yes, you could all be Hulks if the mood strikes you - it will also make Tachyon Rift Missions appear more frequently and be scaled for Power Levels from 1 through 100. If you can complete them, the missions will also give out event-specific rewards.
It's handy that the Tachyon Anomaly is causing enough dimensional disturbance to let heroes team up with themselves, especially since letting players double (or triple or quadruple) up on the same heroes has been a frequent fan request since launch. Only allowing one of each hero keeps things closer to the comic book/cinematic vision of heroic teamups, but it can also be frustrating if you really want to play one hero in particular and just can't seem to get into a team while using them.
The roadmap also goes into a little bit more detail about the upcoming War for Wakanda expansion, which will introduce Black Panther into Marvel's Avengers for the first time. The new content will include a new Wakandan Jungle biome, a new Outpost to check out, and a Power Level cap increase for all of your heroes - the developers are already calling it "the biggest content drop since launch." It's set to arrive sometime in 2021.
The PS5 and Xbox Series X versions of Marvel's Avengers are out now.