There's been nothing official from the game’s developer yet, but a Microsoft update has detailed the next batch of downloadable multiplayer content for BioShock 2.
According to Microsoft the Rapture Metro Map Pack will be available for download from April 29th for 800 MS Points (approximately NZ$15). Reportedly, the pack includes six new multiplayer maps, a new multiplayer game mode, two new masks and three new achievements.
The new multiplayer game type is called Kill ‘Em Kindly, reportedly with a strong focus on melee combat.
Although this information pertains to the Xbox 360 version of BioShock 2, presumably the DLC will also become available for both PC and PlayStation 3 at the same time.