A TV spot for Thunderbolts* confirms Lewis Pullman's Sentry is stronger than all of the Avengers, and he's in the cast of Avengers: Doomsday.

Part of the reason why fans are so certain about this theory is because concept art from Avengers: Doomsday leaked online which seemingly showed variants of She-Hulk and Hulk. Marvel security is notoriously tight, so the fandom is really running with what limited information it has about the project.

MCU fans aren't sure what to make of new rumors about Scarlet Witch and She-Hulk's potential appearances in Avengers 5 and 6.