As part of the large Cataclysm information released tonight, we've gotten quite a bit more information on how raids will be changing. One exciting idea is "downshifting," namely, the ability to split a 25-man raid up into separate 10-mans. There won't be any sort of "upshifting" allowed, however. Simply put, if your 25-man fails to proceed due to numbers, it can break up into separate 10-mans with the same bosses defeated as the 25 was at the time of division, and if you later get those other players back, another 10-man can be created with the same conditions.
In addition, raid lockouts will be more forgiving; as long as you have killed the same bosses as the raid in question, you'll be able to join a raid in progress even if you've been in a different raid to the same instance during the lockout. Basically, you will not be able to kill the same boss twice during a lockout, but you won't be totally cut off from raiding with others simply because you were in a different raid lockout earlier that fell apart, as one example.
Both these changes seem directly aimed at increasing flexibility in response to the shared lockout between 10- and 25-man raids in Cataclysm, and personally I think they go a long way towards addressing concerns I had with that concept. Anything that increases, rather than decreases, the available raid options is an improvement. In addition, "There will be more 'Algalon-style' encounters for both 10- and 25-player heroic modes which will offer loot a half-tier better than the rest of the instance."
But there's more than just changes to raid lockouts and hard modes: We also have new details on two new raids coming with Cataclysm, Grim Batol - The Bastion of Twilight and Skywall.
The Bastion of Twilight is intended as an entry-level raid, with five encounters and an optional sixth boss at higher difficulty. The end boss is Cho'gall himself, and apparently defeating him on heroic will trigger a floor-collapsing lore revelation described as a "horrifying secret" by Lead World Designer Alex Afrasiabi.
Skywall will feature a 5-man instance, Vortex Pinnacle, where you can use your own flying mounts to travel (but apparently no vehicle or flying mount combat of any kind) and a raid that will include players going up against Al'Akir the Windlord.
All in all, a fair amount of new raiding information to whet anyone's appetite for news. I'm actually much happier about 10- and 25-man raids dropping the same gear now; it really sounds like the added flexibility will smooth out any bad patches in transition, and the new raids sound fascinating. What could possibly lurk under Cho'gall's floor?
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From goblins and worgens to mastery and guild changes, it's all there for your cataclysmic enjoyment.