Doctor Strange in the Multiverse of Madness will narratively connect to Spider-Man 3. The Doctor Strange sequel, directed by Sam Raimi, is bringing back Benedict Cumberbatch's sorcerer with a much bigger mission at hand with his story connecting to other MCU projects including Jon Watts' upcoming Spider-Man film.
Officially announced at San Diego Comic-Con 2019, Doctor Strange in the Multiverse of Madness is set to fully explore the existence of MCU's alternate dimensions—some of which were created by the time heist in Avengers: Endgame. It's been previously confirmed that the Disney+ shows such as Loki and WandaVision will connect to the sequel, with Elizabeth Olsen's Scarlet Witch set to appear. But now, it's been revealed that it will also narratively connect to another MCU movie in the untitled Spider-Man 3, pretty much confirming rumors that Doctor Strange will appear in the Sony/Marvel threequel.
MCU architect Kevin Feige appeared at Disney's Investor Day presentation and announced that the production for Doctor Strange in the Multiverse of Madness production is in full swing in London. On top of that, he also confirmed that the sequel will have narrative connections to Spider-Man 3 which has been rumored to be Marvel Studios' attempt at live-action Spider-Verse.
Spider-Man 3 is also currently in production in Atlanta, Georgia, which means that work on it and Doctor Strange in the Multiverse of Madness are overlapping. Before filming began for the threequel, however, news broke out that Benedict Cumberbatch will appear in the film on the heels of reports that Jamie Foxx is making his Marvel return as Electro from The Amazing Spider-Man 2 movie. Then it was announced that Alfred Molina would return as Doctor Octopus as well. Between these two casting developments and J.K. Simmons also returning as J. Jonah Jameson in Spider-Man: Far From Home, the public has been convinced that Spider-Man 3 will be an important part of Marvel Studios' efforts to build their multiverse. Whether or not Cumberbatch actually shows up in the film is currently unconfirmed, but Feige's latest announcement convinces fans all the more that this will be the case.
As exciting as the confirmation is that Doctor Strange in the Multiverse of Madness and Spider-Man 3 are narratively linked, this begs the question: what will happen to the storyline set up at the end of Far From Home where Spider-Man's real identity has been outed? Aside from that, the young hero is being accused of killing Mysterio after The Daily Bugle broadcasted a heavily-edited video of Quentin Beck in supposedly his final moments. The multiverse is already a complicated concept to tackle and introducing any other subplots could lead to a stuffed film that is convoluted and not good. This is something that Marvel Studios and Sony should be cautious about.