Contrary to what happened with the Marvel TV shows on Netflix, this new batch will be directly connected to the movies in the MCU, to the point where fans will have to keep up with them in order to fully understand the movies. First off is Doctor Strange in the Multiverse of Madness (with Scarlet Witch making an appearance in the movie) and bringing back characters who died prior to Avengers: Endgame.
As the title says, WandaVision will see the return of Vision (Paul Bettany), who died in Avengers: Age of Ultron. Here are the dead MCU characters who can return in WandaVision.
Vision
WandaVision will take Scarlet Witch and Vision to different decades and thus will have different sitcom styles. This hints at the series being based on Wanda’s reality-warping powers, which would make it possible for her to bring Vision back in some way and jump from one decade to the other, building a life with him in each one. It’s possible, however, that Scarlet Witch could bring Vision back for real in some way, whether through her own powers (which are derived from an Infinity Stone), through time travel, or by bringing Vision from another timeline in the multiverse, thus connecting with (and possibly kickstarting) Doctor Strange in the Multiverse of Madness.
Quicksilver
Scarlet Witch’s brother, Quicksilver, was introduced in Avengers: Age of Ultron but didn’t stay for long. Quicksilver didn’t make it out from the Battle of Sokovia alive, adding more heartbreak and loss to the life of Scarlet Witch. Age of Ultron’s Quicksilver was played by Aaron Taylor-Johnson, and at the same time, the character was being played by Evan Peters in Fox’s X-Men movies. Aaron Taylor-Johnson’s version to appear, once more thanks to the multiverse.
Ultron
With Vision back, is very possible that Ultron could be an illusion that brings (more) chaos to the warped reality, the version of another universe, or Scarlet Witch could resurrect him subconsciously while bringing Vision back.