They'll be cranking out Batman games until we are sick of them and then pump out a few more after that. Batman: Arkham Origins proved WB could use another studio tomake an okay facsimile of the Rocksteady style. Personally I will be okay with a non-Rocksteady Batman game set in a different Earth (is it Marvel that uses universes and DC that uses Earths for alternate realities or vice-versa?) using the Nemesis system from Shadows of Mordor.
I think at most WB can do one more game in that Rocksteady style before they have to drastically change things up with entirely new game play mechanics.