Snydri has come out with a very clear, very concise statement: Wrath of the Lich King will be playable at 9:00pm PST on all North American and Oceanic realms.
This differs significantly from previous statements by blues that have said that Wrath will be playable based on your time zone.
Additionally, there are reports that people have already gotten into Northrend on the EU servers. Quite a bunch of lucky folks.
But for the majority of us here in the states, we'll be seeing you at 9:00pm PST / 12:00am EST in Northrend!