Batman: Return To Arkham will not be releasing next month. The news this morning coming straight from the horses mouth as the devs took to their forums to explain themselves to fans...

After reviewing the progress of the project, the team at WB Games has decided to delay the release of Batman: Return to Arkham to give the team at Virtuous Games additional time to deliver a polished Batman Arkham game experience.  We do not have a release date yet and will be sure to communicate that once we are sure the game will be ready.   We know this is disappointing news, but we feel the extra time will allow the team to create the best gaming experience for our fans. 

While no specific reason was given, the game was not present at E3 and it's likely that the game has been reworked after a graphical comparison video showed the graphics could be worse between the remastered PS4 version and the PS3 version.

I think it's good WB will be doing right by the fans. Considering this is around the 4th time this series has been re-released I would hope the latest installment would indeed be the definitive version. There's a lot of good stuff coming out this year so we can handle the wait!