This seems to rather conclusively rule out the possibility of a new Batman: Arkham game- that said, that doesn’t mean that there won’t be a new Batman game in that vein, period.
I am sure that many want a new Batman game (beyond just the Telltale ones, I mean)- so hopefully, that is something that ends up happening.
In fact, it is entirely possible that a new Batman game is developed by Warner Bros., but just that it is not branded Batman: Arkham.
However, if Kevin Conroy, famed voice actor of Batman (and not just in the games, but across the animated series, movies, and more) is to be believed, there will be no new Batman: Arkham game.