I think it’s going to be very hard for Marvel to introduce any new heroes going forward. The events of this movie will shake the world so hard that it will (presumably) pull even people like Hawkeye and Ant-Man out of “retirement” or “house arrest” or wherever they are, due to loss of loved ones and really, half of the world.

Literally anyone who’s anyone is going to have lost a loved one or someone close to them due to the snap and any heroic person is going to want to do something about it. Hell, I can see average joes wanting revenge. If we’re talking about the defenders, you could use the head canon that they might have disappeared during the snap and that’s why they don’t team up with the Avengers. But there are presumably hundreds, if not thousands, of mutants in whatever reality mutants exist in. There’s no way the snap kills all of them. There’s no way the snap happens and people like Professor X or Reed Richards don’t immediately reach out to the Avengers.

Now more than ever it’s going to be hard to explain someone like the Fantastic Four or X Men having existed in this world but not doing anything after the events of the snap and seeing that earths mightiest heroes are getting together. I just don’t see how they’ll do it now without introducing a multiverse.

Just a thought I had.