The Rocksteady studios are working on a new project, but what’s in the making is unfortunately not yet officially known. Some time ago, the developer said that the title would blow us away. Speculation goes in the direction that the studio after Batman deals with Superman.
Rocksteady is actually working on a Superman game in an open world (Metropolis), according to a recent rumor stemming from 4Chan (so be skeptical). The area will be three times bigger than in Batman: Arkham Knight. It uses the Unreal Engine 4, Brainiac is the main enemy and the title takes place in the Arkhamverse.
And it goes even further because Rocksteady and WB Montreal to work together on a Justice League multiplayer game. The Superman title, which will be announced in the coming weeks, has priority, however. But as I said, you should record the rumor with some caution.