In hopes to capitalize on the movie’s hype, I imagine.
The re-release of Batman: Arkham Knight will have the Batman vs Superman: Dawn of Justice themed DLC included in the box, it seems. The DLC itself is nothing special, of course- it’s just the Batsuit and Batmobile from the upcoming movie, which stars Ben Affleck as Batman in the first joint appearance of Batman and Superman on screen.
This won’t be the only DLC that the re-release includes in the box, of course- but it’s the one that’s getting top billing (including a pretty prominent sticker right there on the box), probably to cash in on the hype of the new movie’s release and boost sales of the game via the re-release that way.
If you haven’t already played Arkham Knight, this re-release will be as good a time as any to pick it up, I suppose. The game is definitely the weakest game in the Arkham trilogy, so do temper your expectations going in. It is available on PlayStation 4 and Xbox One. There is also a version for the PC, but that one is so fundamentally broken, it does not merit being dignified with a mention.