Batman Arkham City GOTY edition coming with new DLC
On May 29 you can pick up the GOTY edition of Batman: Arkham City which includes all of the DLC up to now, plus a new DLC pack "Harley Quinn's Revenge"
In Harley Quinn's Revenge (available as DLC also on May 29), you allegedly get to use Robin in the main game map. No word on if you have to have the Robin DLC already for that to work.
If you don't already have this game, you should definitely pick this up. Best. Game. Ever.