Blizzard has released a series of background information pages on the Gnomeregan and Echo Isles campaigns to be happening with the coming Cataclysm expansion. We've known for a while that this pre-cursor world event will be happening, and it's nice to see some official information come out about it.
For those looking for the datamined material, check out the following heavy spoilers:
Of course, it's important to remember that these transcripts were taken from the PTR and could easily be changed in upcoming patches. Nothing is set in stone until it happens.
The full Blizzard announcement is as follows:
Nethaera -- An Assault on Two Fronts
Regarding "Patch 3.9" High Tinker Mekkatorque, betrayed by Mekgineer Thermaplugg and forced to flee the irradiated city of Gnomeregan with the few of his fellow gnomes who managed to survive, is preparing to reclaim his once glorious city. Meanwhile, in distant Durotar, Vol'jin of the Darkspear trolls is determined to exact revenge upon the witch doctor Zalazane for dividing the Darkspears and seizing the land bestowed to them by Thrall: the Echo Isles. Read more about the ongoing struggles of the gnomes and the trolls... and their plans to seek redemption.
: 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.