Yeah but I think Feige is gonna use this opportunity to bring in as much new and/or AU characters as possible. I think that has to do with why Derrikson left, he wanted to make it just about Strange and his supporting characters like the first movie.
Well I think that the only characters that are gonna appear for the first time in WandaVision will be Agatha, Billy and Tommy, and whoever the villain is(Chthon, Nightmare, Grim Reaper. Someone like that). Mutants showing up is bs. And the Doom thing was made up by that weird troll.