While the long-time rivalry between DC and Marvel Comics may be an anachronism in terms of any tangible exchanges between the publishers, it does seem there is one area in which the publishers are still battling, even if just coincidentally.
Both publishers (and the Hollywood studios that adapt their stories) are seemingly going all-in on the Multiverse at the exact same time.
Similar to a phenomenon that is referred to by the term 'twin films,' that's when Hollywood develops and releases very similar projects within a short time with of another, like once upon a time when they made 'twin films' about giant meteors threatening the Earth and erupting supervolcanoes. More recently Olympus Is Falling and White House Down were action films depicting terrorist takeovers of the White House both released in 2013.
Multiverses will be 'twinned' at Marvel and DC for the foreseeable future in a variety of projects.
The 'Marvel'ous Multiverse
Marvel Comics just announced Avengers Forever - a new version of the well-regarded 1998 Kurt Busiek-Carlos Pacheco 12-issue series that teamed a disparate group of the Earth's Mightiest Heroes plucked throughout their history to combat Immortus, a version of the time-traveling tyrant Kang from a variant timeline.
This new ongoing Avengers Forever by writer Jason Aaron and artist Aaron Kuder appears to be deviating from the formula a couple of degrees - instead focusing on various Avengers throughout the Multiverse (the "Multiverse’s Mightiest Heroes") including an archeologist Tony Stark who is the "Invincible Ant-Man" rather than Iron Man.
Marvel is even more multiverse-preoccupied on the film and TV side, with 2019's Avengers: Endgame, 2021's Disney Plus series Loki (which introduced Kang and a Kang variant He Who Remains to the MCU), the current What If…?, December's Spider-Man: No Way Home, March's Doctor Strange in the Multiverse of Madness, and 2023's Ant-Man and the Wasp: Quantumania (which will also feature Kang) all focused on variant timeliness and multiverses, which Marvel seems to be blurring the line between.
The Multiverse in fact appears to be the leading candidate to serve as a narrative throughline for the MCU for its next phases the same way the Infinity Stones were for the first four phases.
DC won't be left behind
On DC's side, its current new comic book 'Infinite Frontier' editorial era is based on the vast expansiveness of its multiverse, which has recently expanded to become an omniverse.
The current DC limited series Infinite Frontier by writer Joshua Williamson will then spin off into the November-debuting limited series Justice League Incarnate also by Williamson, which stars a Justice League featuring characters from around its multiverse, which includes a couple of 'variants' (President Superman, Aquawoman) of core Justice League members Superman and Aquaman.
If Justice League Incarnate sounds like it shares some conceptual DNA with Avengers Forever, you're right on the money. To be fair, Justice League Incarnate was announced first, but both were almost certainly developed separately and without knowledge of one another.
And not for nothing, but Justice League Incarnate will also star a new character Dr. Multiverse, who is from DC's Earth-8; a multiversal world that's more or less DC's version of the Marvel Universe.
And Justice League Incarnate is only part of the second act of an 'Infinite Frontier saga' that seems to be headed towards a Darkseid-focused new Crisis - the latest offshoot of the granddaddy of all comic book Multiverse stories, Crisis on Infinite Earths.
For their part, WarnerMedia is also knee-deep in DC-adapted Multiverse projects.
The entire CW-DC TV world is based on the Multiverse foundation and given Warners boldly connected the TV world to the feature film world in its event crossover adaptation of Crisis on Infinite Earths when Ezra Miller's Flash made a cheeky cameo, there's every reason to suspect the CW shows and films co-exist in the same multiverse with its HBO Max streaming series like Titans and Stargirl.
And of course, Miller's Barry Allen/Flash gets his own feature film in 2022, which is adapted from the DC Flashpoint event series all about an alternate, variant timeline. The film will guest star both Michael Keaton and Ben Affleck as their versions of Batman from different film series and that's likely just the tip of the iceberg of the variant timeline/multiverse shenanigans The Flash will be steeped in.
And oh, by the way, the Flashpoint Batman (Bruce Wayne's dad from a timeline in which Bruce and Martha Wayne were killed in Crime Alley) is a prominent character in the comic book Infinite Frontier and Justice League Incarnate series.
Plus there's the animated film adaptation of the popular DC game Injustice, which takes place in a variant world in the DC Multiverse in which the Joker tricks Superman into murdering a pregnant Lois Lane and millions of people in Metropolis, which transforms him into a ruthless tyrant.
A Multitude of Multiverses
So for fans and readers who cross boundaries for comics from both publishers and the films and TV shows adapted from their stores, they're going to be seeing a lot of the concept for the foreseeable future. Multiverses are more or less distilled fan service steeped in what Stan Lee called the "illusion of change," so it'll be interesting to see how big an appetite for Multiverses exist while Marvel and DC both serve big heaping portions of it simultaneously.
Not that the Multiverse is a Marvel or DC invention. Star Trek's Mirror universe with its bearded, evil Spock was an earlier genre/pop culture breakthrough that proved the mettle of the premise among fans.
More recently Sony's highly-regarded Spider-Man: Into the Spider-verse demonstrated critics and even mainstream audiences will embrace the concept, and likewise, Loki seems like a hit among both hardcore Marvel fans and more casual MCU fans.
The question now isn't 'Will fans dig the Multiverse?'; it's more like 'How much is too much?' or if that's even a thing.
There are likely alternate timelines in which fans embrace it all happily and timelines in which they might get a little exhausted from it all, and we'll find out which is our 'sacred' timeline soon enough.
Newsarama explains the Marvel Multiverse and the meaning of Earth-616.