For Xbox One
[Update: It seems that they've changed the date listing to read "Not announced" since this morning. Tease.]
We found out that Batman: Arkham Knight was delayed right before E3, and last week we learned that the wait might not be as long as we originally thought. I think 2015 is a long time to wait no matter how you look at it.
If a new posting on the Microsoft Store is was correct, we'll only have to wait until February 2015 to start playing. Well, on the Xbox One, that is.
Between this and the earlier bit from the voice actor, I think we can count on an early 2015 release.