Kisirani, your friendly neighborhood world designer, replied to a comment in the general forms today where a player said he'd be disappointed if there wasn't a Cataclysm launch event. Kisirani replied:
*rolls up her sleeves and idly kicks the crates from last launch event under her desk*
We're on it.
That's confirmation in Blizzard speak.
Will it be as badass as the Lich King launching his forces into Stormwind, Orgrimmar, and the rest of Azeroth? My guess is that it'll be at least 37 times as badass.