Ever since Batman: Arkham Knight launched in the summer of 2015, fans of Rocksteady Studios have been waiting to see what the critically-acclaimed development team is going to do next. Rumors have been swirling for years about Rocksteady's next project, with the latest one claiming that the mysterious game could possibly be revealed at E3 2019.
The rumor stems from a post on ResetEra by Hasan Ali Almaci. Almaci is a "freelancer" who claims that Rocksteady's next game will be announced either in early 2019 or at E3 "depending on milestones they meet." Almaci stopped short of going into specifics about Rocksteady's game, but did suggest that it is not a Marvel video game, so presumably it's working on another title based on a DC Comics character.
Another entry in the Batman: Arkham franchise is certainly possible, but the most persistent rumor has been that Rocksteady is working on a Superman video game instead. Given Superman's tumultuous history with the games industry (Superman for the Nintendo 64 is often listed as one of the worst games of all time) and the challenge of making a basically invincible character fun to play as, it would certainly be interesting to see Rocksteady's take on the Man of Steel.
Past rumors have indicated that the Superman game supposedly in development at Rocksteady Studios is subtitled World's Finest, and it will feature an open world with Brainiac as the main villain. Combat will apparently be similar to the Dragon Ball Z games, and the game is said to be set in the Arkham universe. Of course, none of this information has been confirmed by Rocksteady, and so fans should take all of this with a massive grain of salt.
While it's impossible to verify if Hasan Ali Almaci is telling the truth about when fans will get to see Rocksteady's next game, the timeline seems about right. Rocksteady likely started work on its next project not long after Arkham Knight shipped in 2015, so the game has been in development for at least three years at this point. If so, then a 2019 reveal and a 2020 release actually seems to be a rather likely scenario.