According to Kevin Feige, the president of Marvel Studios, the Marvel Cinematic Universe is about to officially become a multiverse. Following the debut of the forthcoming Doctor Strange in the Multiverse of Madness, which is tentatively scheduled for a theatrical release in early spring, the MCU will continue to explore that movie's themes.
As per Feige, what this means is that it plans to approach the basic concept in the "most direct way." Speaking on the subject in a conversation with Rotten Tomatoes, Feige was typically vague, but what it means is that, as Marvel continues to move into its strange post-Evans, post-Downey period, it may be approaching the age of the unified Marvel Cinematic Multiverse.
This would track with the early reports that Jamie Foxx and Alfred Molina will appear in the third Spider-Man movie later this year, playing the parts of Electro and Doctor Octopus from the two earlier Spider-Man film series. Much in the spirit of something like Doom Eternal, then, the MCU (MCM?) may very well be entering a period where it feels comfortable drawing upon all of Marvel's scattered continuities.
The multiverse is a recurring theme in the MCU's source material. Back in 1977, Marvel released a monthly series called What If? dedicated to exploring what might've happened if various landmark comic stories had ended in a different way. The comic, which also lends its name to a forthcoming animated series on Disney+, had a second volume in the '90s that quickly became notorious for its high protagonist body count.
Since then, the concept of the multiverse has frequently shown up in the comics, as an excuse to resurrect dead characters or provide fresh villains. For example, in the current Guardians of the Galaxy comic, two of its frontline characters—Phyla-Vell and her wife Heather—are the last survivors of a destroyed alternate timeline. Also, in the current volume of X-Factor, Rachel Summers is a refugee from a dystopian future that's since been prevented from coming to pass.
The most obvious inspiration here, however, may be the relatively recent Spider-Verse crossover, which in turn inspired the Oscar-winning animated film Into the Spider-Verse. In it, every version of Spider-Man that has ever existed, from the self-aware, fourth-wall-breaking animated Ultimate Spider-Man to the square suit-wearing dope from the 1968 cartoon, teamed up to repel a threat from a universe-crossing band of supervillains called the Inheritors.
The Avengers have had a similar arc, 1998's Avengers Forever, which pulled in characters from the Avengers' entire history to fight the time-traveler Kang the Conqueror. With the recent revelation that Jonathan Majors (The Last Black Man in San Francisco) is playing Kang in the third Ant-Man movie, this may serve as additional evidence that the next stage of the MCU is going to turn into a Doctor Who-style trip through space and time.
Doctor Strange and the Multiverse of Madness is planned to hit theaters on March 25.
Source: IGN