Avengers: Endgame saw the introduction of Iron Man's daughter, Morgan Stark. Katherine Langford was originally cast as the older version of Morgan, however the scene was later cut from the film.

Doctor Strange in the Multiverse of Madness introduced the concept of multiversal travel, thanks to the abilities of America Chavez. With that in mind, it makes sense that we might get to see Robert Downey Jr. return as an alternate Tony Stark.

This trailer imagines Morgan Stark trying to figure out multiversal travel. With the help of Peter Parker, who she spots in an old photo, she is able to figure out how to travel between universes. Initially, this allows Peter to see alternate versions of Tony as he visits him at different moments in time. Eventually, they figure out how to allow someone through to their own universe. And so Iron Man is reborn!