Several reports have poured in from Bioware Social users that the new Mark of the Assassin DLC has been released early, and is available for purchase and download. Several PC users have downloaded the DLC and reported that is in full working order, though the new content has been removed from Xbox LIVE Marketplace. It is currently unknown what the current situation with the Playstation Network is.
Update: These characters supposedly appear in the DLC:
If Leliana and Teagan have already been encountered, they will mention it in dialogue.