Microsoft announced at this year's E3 that it has reached an agreement with Capcom for timed-exclusivity when it comes to Resident Evil 6's DLCs. While we still don't know what they are exactly, it seems it will comprise of a few game modes at the very least.
In a product listing for Resident Evil 6 at Xbox.com (via Eurogamer), it lists:
3 new modes exclusive to Xbox 360 coming soonMicrosoft will announce 3 timed exclusive modes for Capcom’s Resident Evil 6 available after the game’s release on 2nd October. Further details TBC
Resident Evil 6 is scheduled to hit on October 2 for the Xbox 360 and PS3.