(There are spoilers for Avengers: Infinity War here, but not for Avengers: Endgame.)
It’s been a long road to get to Avengers: Endgame. We’re over a decade into the MCU now. Thanos took out half of the living creatures in the universe, and our heroes are trying to deal with the aftermath. Whatever happens in the new film, (we know and aren’t going to say to preserve the mystery), we are aware of upcoming films like Spider-Man: Far From Home and Black Panther 2, so we know that the universe lives on, whether or not every hero comes with us. It would be hard to up the ante after something so huge, so it’s likely that some of the upcoming movies are going to deal with smaller threats, like we saw in Spider-Man: Homecoming or Ant-Man and The Wasp.
In a universe with this sort of continuity, it’s likely that villains from the past might reappear. If you’ve been reading comics for a long time, you know how frequently it happens. Hey, sometimes they even come back from the dead. We may have forgotten about them in light of Thanos and his actions, but we just saw it in Avengers: Infinity War. Did anyone see Red Skull coming? His role as gatekeeper took out one of our favorite characters and allowed Thanos to make a decision that would let him win. It’s more of a passive role than we’re likely to see in the future from other villains, but he reappeared when we least expected it all the same. It could happen again, and it would be surprising if it doesn’t.
There are a number of villains that might reappear, depending on who is getting solo films in the future (please give us Ms. Marvel), or whatever is going to happen with Marvel TV now that we have the new Disney streaming service on the way. Maybe villains will cross over, especially if they aren’t just doing solo films in Phase 4. What if the Abomination from The Incredible Hulk returns? Emil Blonsky has Super Soldier Serum and Bruce Banner’s blood in his veins. Sure, he’s unlikely to be part of a solo film, and honestly, probably won’t reappear, but he could. Ten Rings seems far more likely. In fact, it’s interesting to speculate on who might end up as part of that organization. What about Justin Hammer from Iron Man 2 if he gets out of jail? Heck, we could see Ghost recruited, despite her change of heart at the end of Ant-Man and The Wasp. She’s pretty fragile, emotionally, and that always makes a good recruit for villainous organizations.
Since we do know that Guardians of the Galaxy Vol. 3 is happening, in whatever form it takes, we might see a certain golden woman, and a man named Adam. Ayesha could certainly come back, as her story was clearly not over. If she survived the snappening, of course. We may have no idea if her creation of Adam Warlock is going to appear in the third film for the team, but it would be surprising if he doesn’t.
We can revisit this after fans have seen Avengers: Endgame, but it’s inevitable that we’re going to see callbacks to earlier Phases of the MCU. You don’t have an 11-year continuity and just abandon it all once you reach the end of a phase. We’re definitely going to see some familiar faces and names once we head into Phase 4 after Spider-Man: Far From Home. It just remains to be seen which ones will pop up again.