Even without any kind of insider info, the title of the next Avengers movie tells you everything you need to know about the basic premise: The Kang Dynasty will see Earth's Mightiest Heroes face-off against Kang the Conqueror and (most likely) a number of his Variants.
The hows, whys and wheres of it all remain to be seen, but we are sure to learn more as we head into Phase 5 (Ant-Man and the Wasp: Quantumania will almost certainly lay some groundwork), and there have been some very interesting rumors doing the rounds over the past few weeks.
The Heavy Spoilers YouTube channel has been the main source of these rumors (their validity is obviously TBD, but previous scoops have panned out), and the show is now claiming that our heroes will gain a surprising ally in the upcoming battle: Nathanial Richards, aka He Who Remains!
We were introduced to He Who Remains in the season finale of Loki, and before he was killed by Sylvie, he claimed that he was watching over the Sacred Timeline in order to ensure his far more destructive Variants were kept in check. Upon his death, it was revealed that he was telling the truth, as the Timeline splintered and gave way to the Multiverse.
Apparently, we will meet this character in The Kang Dynasty before the events of Loki (though we know time works very differently for this guy) when he still goes by Nathanial Richards. He is said to join forces with the Avengers to take on Kang the Conqueror, and their alliance will continue on into Secret Wars when he helps the team assemble other heroes from the Multiverse.
Remember, The Kang Dynasty is still more than two years off, so none of these rumors should be taken at face value. Still, it's an undeniably intriguing prospect, we're sure you'll agree.