According to the in-game ticker we’re getting new free DLC for Batman: Arkham Asylum. The ticker states that the content is coming in 9 days (which I think makes it Thursday September 17th). I can’t confirm if this is for the Xbox 360 version too but I would imagine so.
So, what do you think it is then? My money is on new costume variants for the challenges but it could easily be new challenges or something even more fun.
Source: In-Game ticker. Thanks, Erroneous