While Batman Arkham Knight was the last hurrah in the Batman mythos for Rocksteady Studios, Warner Bros. Interactive is going to continue publishing DC Universe and Batman games in the future. So while Rocksteady will not be working on these titles, it is very likely that Warner Bros. Games Montreal (via IGN) will be the studio that makes the next Batman or DCU-themed games for the publisher.
The IGN report uncovered some job postings at WB Games Montreal’s official site. The studio behind Batman: Arkham Origins revealed that the company is developing two AA projects that are
“focused on expanding the DC Comics universe in the interactive space.” The jobs available include software developers, programmers, artists and designers.
There are no details yet on what the projects for WB Games Montreal are working on. From a logical standpoint, Batman: Arkham Origins did leave things open for a potentially awesome Suicide Squad game. Warner Bros. Pictures is trying to turn Suicide Squad into a big franchise with a new movie next year, so it would make sense if one of the games goes in that direction. There was speculation earlier this summer that a Superman video game could be in the works too. However, nothing is confirmed at this point.
WB Games Montreal did develop the Batgirl: A Matter of Family, which was a story-driven DLC for Batman Arkham Knight. So they have had some recent activity beyond Arkham Origins.