Doctor Strange In The Multiverse of Madness is set to be released in theaters next year but the film itself will receive its first trailer before then. Since Doctor Strange will be in the upcoming Spider-Man sequel it will make sense for the trailer to be released following the movie considering his movie releases afterward.
The Spider-Man: No Way Home trailer teased the possibility of the real existence of a multiverse and with the ending of Wandavision it seems the pieces are in place to bring a long list of new Marvel characters. If Spider-Man is supposedly able to bring in villains from the films that technically don't fit in the current Disney canon, then that means anything is possible for other characters moving forward. That coupled with the involvement of Doctor Strange and Wanda Maximoff, then the possibility of rewriting reality is even more possible.
The rumor says the trailer will release in December which is right around the release of the upcoming Spider-Man sequel. This rumor comes from Daniel Richtman (via Comicbookmovie.com) which doesn't mean that it's confirmed or official but it does make sense. In actuality, this sounds more like a guess than it sounds like 'insider information.' Since the Spider-Man film precedes the Doctor Strange film then of course Marvel would couple the Spider-Man release with promotion for the upcoming next Marvel film so this 'guess' or 'rumor' isn't anything unique.
Fans should also keep in mind the possibility that the Doctor Strange sequel can also be delayed again. Considering it was pushed back due to the pandemic, filming as well as production scheduling was halted for Marvel at one point so they're just starting to get ahold of their releases by consistently putting out content in both theaters as well as on their streaming platform Disney plus.
This film is set to break boundaries by utilizing the multiverse. The multiverse means alternate versions of characters can return (which means a potential return for many veteran actors) as well as introductions of new versions of characters. This may be how Marvel reintroduces the fox characters (X-men, Fantastic Four, and Doctor Doom). Many expect the multiverse to be the way in which the X-men or mutant strain are introduced but of course, it's all speculation. This may also be how they introduce Miles Morales into the film but only time will tell.
Doctor Strange In The Multiverse of Madness is slated for a March 25th, 2022 release
Source: ComicBookMovie.Com