The mid-credits scene saw Clea announcing to Doctor Strange that he had caused an incursion that they needed to team up to fix before they both jumped through a portal into what looks like the Dark Dimension.
Let’s not forget that having used the Darkhold, Stephen now has the ability to open a third eye on his forehead.
Sinister Strange could do this too since he was corrupted by the Book of the Damned when using it, so could this happen to Earth-616’s Avenger too?
Possibly, although Scarlet Witch did destroy every copy across the multiverse, so maybe he’s in control of this new power.