Rocksteady Studios is potentially working on a Superman video game as their next project. This is according to a listing on GameSystemRequirements website.
While this is by no means is a confirmation of the game, it is interesting to see this after all the rumors of a Superman video game being in development at Rocksteady Studios. This listing also appeared just before the launch of The Game Awards, which are going to have 10 new game announcements.
The listing is still available on GameSystemRequirements where the developer is listed as Rocksteady Studios. The genre is Action, Adventure while there is no more information available on it.
GameSystemRequirements mostly deals with PC games and their system requirements. It also had a listing for Devil May Cry 5 almost a month before the official announcement, so it is entirely possible that this is another leak. Still, it is best to approach this as a rumor and taken it with a grain fo salt.
Rocksteady Studios last worked on Batman Arkham Knight which was released back in Summer 2015. Since then, they have been quiet on their next project despite all the rumors about it being a Superman video game. There were also plenty of teasers in the previous Batman games that hinted at a Superman, but they could be simple easter eggs.
In any case, if you want to see an official announcement for it, that might happen at The Game Awards which will start on December 6th.