Today [tomorrow in Europe -Ed], World of Warcraft will be torn asunder by a very angry dragon called Deathwing - weeks ahead of the 7th December Cataclysm expansion launch.
In patch 4.0.3a (due later), The Shattering will transform Azeroth as we know it; sprouting lush life in an unlikely Desolace and goring a great scar through The Barrens. And much more.
Most Cataclysm content will be available bar the new zones, races, ability to fly your mount in Azeroth and level 80+ quests and loot. You can even watch the new Cataclysm cinematic when you load World of Warcraft.
Blizzard decided to unleash The Shattering now to allow new class-race combinations - dwarf mage, for instance - time to level in preparation for Cataclysm. You can also pay Blizzard to change your race. So, now is the time to stop being a gnome mage and start being a dwarf mage.
Patch 4.0.3a will remove the elemental portals from the capital cities. Blizzard has temporarily made these permanent so that any loose ends can be tied up within them.
One more thing: it appears that Chromaggus - a Blackwing Lair boss no less - can now be tamed by Beastmastery hunters! WOWInsider says this is doable on the WOW test realm right now.
Blackwing Lair was the second 40-man raid added to World of Warcraft (Molten Core was the first). Chromaggus, a giant dog (and part of the exotic Core Hound family), used to require 40 level 60 players (top-level back then) to kill. He won't retain that power after being tamed, but will be able to access useful ability Ancestral Hysteria. And he's purple.
World of Warcraft: Cataclysm will be released worldwide on 7th December. Blizzard laid out its launch event plans yesterday.