No official announcement has been made, but it is looking highly likely that we will not see Batman: Return To Arkham until November at the earliest. Eurogamer has several sources saying the game will not make it's originally rescheduled date of July 26 due to frame rate and performance issues the port is having. Virtuous Games is handling the port of the game.
Like I mentioned earlier this is still a "rumor" but from the way Warner Bros. is acting we can definitely be assured we will not be seeing this game before Summer's end.
Honestly, it's not like that's a bad thing. It's not like we haven't seen a couple remaster's for this game already. If it were a new game I could see a bit more panic to make sure it gets out to consumers, but until then I think we are all fine playing the original game and waiting for a proper remaster.