Capcom officially announced today that they are planning to release a set of downloadable content shortly after the launch of Resident Evil 6 next month. The pack will reportedly include three new multiplayer modes.
The first new mode will be called Survivor's Mode which is your basic last-man-standing deal, but with the added catch that once you're dead you respawn as an infected, attempting to kill players. If you're able to kill two players you'll respawn as human again.
The second mode is called Predator Mode in which all players cooperate to try to take down one beastly AI enemy. The final mode is called Siege Mode and pits two teams against each other as one attempts to protect an AI NPC, and the other tries to take said NPC down.
Capcom isn't letting loose exactly when the DLC will be launching, but has said that all of these modes will support six players and will use maps from the Mercenaries pool. They've also said that further Mercenaries maps are in the works for DLC as well.
As per Capcom's timed-exclusivity agreement with Microsoft, all DLC will be coming to Xbox 360 first.