According to a recent Twitter feed, Batgirl will star in her own prequel story available in new DLC. Also, the Season Pass will allow players to drive different versions of The Batmobile, as well as apply various skins for Batman, Robin, Nightwing and Catwoman.
The Batman: Arkham Knight Season Pass will run £32.99 / $39.99, or you can get the Premium Edition for £87.98 / $99 on PS4 and Xbox One. With the pass, you can get six months worth of DLC content.
Batman: Arkham Knight comes to PC, PS4, and Xbox One on June 23, 2015.