Take all rumors with a grain of salt, but this one has persisted. For years people have wondered what Rocksteady, makers of those wonderful Batman Arkham games, have been up to. Even the release of Batman VR wasn't enough to calm the rumor mill. Switching between a Superman game and a Justice League game, it seems the prevailing winds still blow in DC's direction.
It certainly has been long enough that whatever Rocksteady has been working on should be, hopefully, ready to see the light of day soon. Currently we seem pointed towards a possible Starro villain and the potential of "seasons" with this Justice League game. However the state of DC and Warner Bros. isn't exactly stable, and perhaps the changing tides has effected this potential title.
Either way I'll keep my fingers crossed. I still think fondly back on Arkham Asylum and wonder what Rocksteady could do with a whole roster of heroes to work with.