Because of the recent rumors surrounding upcoming films, both the Marvel Cinematic Universe and the DC Extended Universe seem to be gearing up for major multiverse storylines. Ezra Miller's solo Flash movie will be Flashpoint-inspired and will see the Scarlet Speedster team up with not only the DCEU's Batman portrayed by Ben Affleck, but also Michael Keaton's Burton-verse Batman. Likewise, the MCU's upcoming Spider-Man 3 will bring back Jamie Foxx as Electro, Benedict Cumberbatch's Doctor Strange and possibly Tobey Maguire's and Andrew Garfield's iterations of the web-slinger. These casting choices all seem to point to the potential of multiverse shenanigans.
Multiverses started off as a fun way for comic companies to bridge cancelled titles from past eras or create a massive crossover event, but now that the movies seem to be planning tons of multiverse events, it has the potential to get overwhelming and tired really quick.
Multiverse storylines, now a norm in the comics industry, could perhaps threaten to make superhero media less accessible. Take the Marvel movies for instance -- they can be complex, fairly faithful adaptations of their comic counterparts, but they also make the universe and story palatable for general audiences who may not be super familiar with deep-cut lore. This accessibility could be seen as the reason why Marvel movies like Guardians of the Galaxy aren't just cult hits, but mainstream successes that often cross the billion dollar threshold. Introducing the concept of multiverses could confuse general audiences, as well as even the most dedicated fan.
This focus on multiverses could also hinder storytelling as they're often times used as a way to fix continuity errors (e.g. Golden Age to Silver Age DC Comics). This often backtracks a story rather than progressing it. By introducing alternate universe characters, the story could get lost in trying to explain its own concepts.
Multiverse storytelling has also been a point of contention with comic fans, with huge crossover events seemingly coming every year across both major comic book companies. If it has become overwhelming for some of the most hardcore fans, then the casual movie-going audience will likely become tired of the trope as well.
Regardless, the possibility of multiverses is intriguing. Many fans have expressed their desire to see Tobey Maguire web-sling one last time, or Andrew Garfield redeem his anti-climatic end. But this focus on multiverses could end up alienating audiences that have shown up time and time again for comic book based movies.
However, Spider-Man: Into the Spider-Verse was able to navigate a multiverse-based story with humor and ease, so there is a possibility that the MCU and the DCEU could pull it off as well. The emergence of cinematic universes changed the Hollywood business model – perhaps multiverse films will have a similar effect.