Not directly Cataclysm related, but close enough. And it's indeed exciting news!
What will change in World of Warcraft after the forced migration?
The core gameplay experience will remain unchanged as a result of the migration. However, you'll be able to take part in all of the new Battle.net features, such as cross-realm, cross-faction, and cross-game chat.
It's like Xfire, in WoW... without xfire!
