With runaway success of Everything Everywhere All at Once, it would be hard to deny that the concept of the multiverse has gone mainstream. Like any sci-fi concept, the multiverse began as real-life speculative science, was interpreted by creators of 'disposable' media, and has finally permeated culture enough that film companies will offer up blockbuster budgets for an idea formerly seen as inaccessible.
In of trying out ambitious sci-fi ideas, comics are more able to experiment that films, and Marvel and DC fans have decades of experience with navigating multiple realities filled with variations on their favorite characters. Likely the most famous example is DC's Crisis on Infinite Earths event, but on any comic stand today, there are still plenty of publications in which a hero is tumbling between dimensions, whether in the pages of Hulk or Suicide Squad. There are a huge number of stories to be told with the idea of the multiverse, but no idea can exist in the forefront of the cultural zeitgeist forever, and eventually the multiverse will have had its day in the spotlight. Marvel and DC need to get out ahead of that process and continue offering readers ideas that mainstream cinema isn't yet ready to engage with.
That's not to say that Marvel and DC need to invent the next big idea, but that in making up the mainstream of comics, they're uniquely placed to build up the multiverse's conceptual successor, giving it the same depth and exposure that has gotten people comfortable with navigating multiple realities in their popcorn fiction. While Marvel and DC have maintained a fascination with the multiverse for decades, comic storytellers haven't been idle, and there are already several concepts which - with more exposure and experimentation - could be the 'next' multiverse.
The Bleed/The Superflow
In a multiverse made up of many realities, there is theoretically a space between those realities. This is what DC refers to as the Bleed and Marvel as the Superflow. Both publishers have explored this idea - in The Authority, the titular team are based on a ship that traverses the space between realities, and Marvel's Secret Wars build-up revealed dangerous lifeforms that live within the Superflow, such as the Builders and Black Swans.
The Bleed is a tandem idea to the multiverse, but it offers some unique ideas that could see it flourish on its own. Beings within the Bleed are often depicted as truly alien to human perception, and they exist separate to every reality, meaning there aren't different 'versions' of them in different realities. This fact was used to great effect in the build-up to Secret Wars, as the various factions who inhabited Marvel's Superflow were presented as a different level of threat to powerful beings who nonetheless exist in thousands of realities - put another way, there are near infinite versions of Thanos, but only one Rabum-Alal.
The Omniverse
The appeal of the multiverse to Marvel and DC fans has always partly been how it accurately describes the process of reading mainstream comics. DC has its regular Superman, a fascist Superman, and a Superman who's a cartoon rabbit, all having their own adventures in their own worlds. Because of this, the idea of multiple realities that can intersect is just an accurate description of following comics.
This advantage continues with the idea of the Omniverse - the term used to describe an infinite multiverse which is still separate to other multiverse. For example, there's a difference between the varying versions of Superman, all owned by DC, and Spider-Man, who's owned by Marvel. Comics like Crossover (from Image Comics) have leveraged this difference to great effect, knowing that it's more exciting for readers to see a genuinely varied cast from different franchises interact than it is for DC to have the Superman of Earth-1 meet the Superman of Earth-5.
Unfortunately, Marvel and DC have so far failed to make the idea of the Omniverse truly exciting or inherently distinct from the multiverse, though DC's Dark Crisis may yet reveal new aspects to this idea that make it truly special.
The Marginalia
Both Marvel and DC feature meta-textually aware characters like Ambush Bug, Deadpool, Doop and Psycho-Pirate who are seemingly undo her murder of the villainous MODOK.
In contrast, DC has most famously used this idea for horror, with the titular hero of Animal Man meeting writer Grant Morrison and learning some hard truths about existence. The idea of a continuity outside continuity (but still not in an actually different reality) is suitably ambitious to work as the next multiverse, especially as characters who can access the Marginalia can also enter and influence true canon, allowing for the same type of crossover appeal. Deadpool has proved this idea can have huge appeal.
Layers of Reality
Many comics - particularly those under the purview of writers like Grant Morrison, Neil Gaiman, and Alan Moore - have dealt with the idea that fiction can be understood as a separate but valid layer of reality. Stories influence the real world, and characters like Superman are likely to outlive the real people who read them. While this idea can be existentially disturbing, it can also be uplifting, and stories like Final Crisis: Superman Beyond (from Morrison and Doug Mahnke) have found new meaning in stories where Superman knows he exists as a symbolic being.
These stories tend to be trippy, but like the multiverse, they describe a fundamental reality of fiction that's worth exploring. Superman is a living being in his own 'world,' but in ours he's loaded with symbolic meaning that stretches beyond individual depictions. The idea of characters who know this about themselves is genuinely fascinating, crossing over with the concept of the Marginalia, but also opening up new priorities in storytelling. Recent X-Men comics have included mental health advice that seems to be as much for readers as for the characters, showing the potential of superheroes whose main focus is trying to help their readers. This intersection between the real and the fictional has an incredible amount of untapped potential.
Omnitime
Omnitime is perhaps the most exciting concept Marvel and DC could embrace as the next multiverse, purely because it's something comics can do better than any other medium. The idea of Omnitime is that all of time is happening at once - like a river, the people within it are swept up by its movement, but those standing on the bank can stroll along, inspecting past, present and future as if they're physical locations. Many creators have observed that this is the literal reality of reading a comic page: all the events are laid out in 'order,' but the reader can go where they like. Influential works like Alan Moore and Dave Gibbons' Watchmen explore this idea, taking advantage of the accessibility of comics to tell stories that depend on the reader's ability to quickly flip back and forward in time. In this story, Doctor Manhattan's inhuman experience of time simply makes him a character experiencing the world in the same way as the reader.
Many series have experimented with this concept, but there's still plenty of ground to cover and experimentation to engage in. Warren Ellis and Declan Shalvey's short run on Moon Knight exemplified how this idea of malleable time can create surprising experiences, with multiple 'scenes' playing out alongside each other on the page, and hidden details that the reader only spots once they flip back in the context of a later moment. This is only a small-scale application, but there are also characters who exist outside time, and whose experience of reality could be explored in far greater depth. Fans are still talking about Doctor Manhattan, so further stories embracing this concept are more than justified.
The Next Multiverse
All these ideas already exist, but what they need to become the next multiverse is a similar level of exploration and experimentation. The 'Big Two' publishers have fleshed out the multiverse over decades, finding many new and different ways to harness the narrative possibilities it offers. Any of the ideas above could have the same level of potential, and allow Marvel and DC to keep offering readers concepts they can't see in the latest wave of blockbusters.
