Batman Arkham Knight has been delayed to June 23rd 2015. It's only delayed by a few weeks this time. Batman Arkham Knight was set to be released last year, but was delayed. We learned that this last game in the trilogy from Rocksteady is rated "M" by the ESRB.
Here is the statement from Rocksteady from Facebook:
"Batman™: Arkham Knight will now launch worldwide on 23rd June, 2015. We're a developer that hates to make any compromises, so we are sorry to say this means it's going to be just a little bit longer until you can play the epic conclusion to the Arkham trilogy. As a reward for your patience and understanding, and to make the wait even more unbearable, we are pleased to whet your appetite with a new gameplay video of Batman™: Arkham Knight.
Thanks so much from everyone at Rocksteady for your continued support. We are working as hard as we can to make you proud.