First and foremost, this will be the next tier of raiding. There was some speculation that this would be an interim tier of raiding, however that is not the case. The gear that will come out of the Crusaders' Coliseum appears to be Tier 9.
Secondly, the encounters will be unlocked one per week until all five encounters are available. This mirrors very closely the way the Sunwell Plateau was handled back in Patch 2.4.
Finally, there will be a new "Crusaders' Tribute" mechanic. The mechanic appears to track the number of times you attempt an encounter, and the fewer times it takes you to complete the encounter, the greater the loot will be for the final boss. A type of raid where you are going for the Tribute rewards will be called a "Tribute Run."
For further information about the upcoming patch check out WoW.com's Guide to Patch 3.2.
The full details of the announcement after the break.