See that image above? Well, it was posted on Batman Arkham's official Facebook page along with instructions to "visit this page on December 31st for a special announcement."
Could it be some Arkham Origin's DLC? A new entry into the series itself, perhaps?
Batman Arkham [Facebook]
I still miss when Lego figures didn't talk, but Lego Batman 3's trailer is cute
12:30 PM on 11.12.2014