This tease might also have something to do with last month’s rumor. In late April, an industry leaker Daniel Richman (behind a paywall, via Stealth Optional) claimed that NetherRealm Studios is currently working on a Marvel fighting game. According to Stealth Optional, he mentioned that the project is now already in the production stage but it’s still not clear whether or not it is actually going to be a Marvel vs. DC fighting game, though.
NetherRealm Studios first worked on a DC Comics-related fighting game Mortal Kombat vs. DC that was released in November 2008. Later, it released a standalone DC game, Injustice: Gods Among Us in 2013. The sequel, Injustice 2, launched in 2017. Despite the games no longer containing a crossover story, Boon and his team added Scorpion and Sub-Zero to each game as DLC guest characters.
Marvel is no stranger to crossover games as well. Since the ’90s, Capcom has worked on a number of Marvel Comics adaptations for the arcades, such as The Punisher and X-Men: Children of the Atom. From there the relationship between both companies blooms and culminates into the release of X-Men vs. Street Fighter in 1996. Capcom then expanded the roster by including a variety of its own and other Marvel characters in the worldwide phenomenon Marvel vs. Capcom series.