Dr. Strange will appear in the MCU's third Spider-Man movie, once again played by Benedict Cumberbatch. He joins a cast that includes Tom Holland, once again playing Peter Parker/Spider-Man, and Jamie Foxx, who's reprising his role as Max "Electro" Dillon from Sony's Amazing Spider-Man films.
The capacity that Strange will play in the as-yet-untitled Spider-Man sequel (Homeschooled? Home is Where the Heart Is? Homebodies?) has not been disclosed, but Cumberbatch is scheduled to start filming the second Dr. Strange movie, Dr. Strange and the Multiverse of Madness, in London at around the same time that Spider-Man 3 is filming in Atlanta. It's probably safe to assume that Cumberbatch will have what amounts to an extended cameo, similar to his one-scene-wonder part in Thor: Ragnarok.
Other returning MCU vets for Spider-Man 3 include Jon Watts, coming back for a third film as director after Homecoming and Far From Home. It's widely assumed but not officially confirmed that Marisa Tomei, Tony Revolori, Jacob Batalon, and Zendaya will all also return for the third movie. Spider-Man 3's script is reportedly to be co-written by Chris McKenna and Erik Sommers, who both have screenplay credits on Far From Home, Homecoming, and Ant-Man and the Wasp.
While next to nothing is known about either Spider-Man 3 or Multiverse of Madness's plot so far, the introduction of Foxx's version of Electro from the Amazing Spider-Man films by Sony to the MCU has been the cause of a lot of fan speculation over the last week. This is the first time a previous live-action version of a Marvel character has "crossed over" to the MCU, so it's hard not to wonder if Electro might be explained as being from an alternate Earth in the Marvel multiverse. This is further fueled by the upcoming debut of the Disney+ series What If?, which will explore alternate outcomes from events in the MCU, and likely by the existence of Sony's dimension-crossing mega-hit Enter the Spider-Verse
Doctor Strange and Spider-Man have a long-standing friendship in Marvel Comics, running all the way back to the original Stan Lee/Steve Ditko run on The Amazing Spider-Man. The characters, both of whom were co-created by Lee and Ditko, first met in 1965's ASM Annual #2, where Spider-Man inadvertently stumbled into a plot by one of Strange's enemies to steal a magical relic from Strange's New York sanctum. Over the next 55 years, Strange has consistently been one of Spider-Man's go-to allies, and vice versa. Cumberbatch's Strange making a cameo in a Spider-Man film, then, has a much firmer basis in canon than newcomers to Marvel might realize.
Spider-Man 3 is scheduled to begin shooting later this month, aiming for a December 17, 2021 release date.
Source: Hollywood Reporter