For those looking for the datamined material, check out the following heavy spoilers:
- Operation Gnomeregan: Transcript and details of the event
- Operation Echo Isles: Transcript and details of the event
The full Blizzard announcement is as follows:
Regarding "Patch 3.9": The URLs above point to these events happening in patch 3.9. It is possible there will be a patch 3.9, however it is also possible the "9" simply stands for "the very last patch before 4.0" (patch 4.0 is the Cataclysm content patch). No one outside of Blizzard knows the right answer, and don't read too much into URLs.
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.