http://www.ign.com/articles/2013/02/12/new-batman-arkham-game-coming-this-year
Time Warner management seems to confirm that the next Batman:Arkham game will be released this year, rather than 2014 as originally expected.
Not that I'm against it in principle, but I'm worried that the dev time will be too short. We were already seeing initial material a year out from Arkham City's release.
That does seem to be a bit soon.
Arkham County? :P
My guess would be the title goes from Arkham City to Gotham City, or City of Fear (following that foreshadowing hint in the Scarecrow Easter Egg).
But they could do another Arkham title that has nothing to do with an area's designation. Arkhampocalypse maybe (following the foreshadowing hints of Azrael's sideplot).