From the WinInfo Newsletter, (which is generally pretty good, IMO):
According to recent internal schedules I've seen, Longhorn and Office 12 are set to arrive concurrently on May 22, 2006. And the first Longhorn beta is set for February 16, 2005--the same beta 1 date I first reported in April. Naturally, this schedule could change--we're talking about Microsoft, after all--but the massive Microsoft infrastructure finally seems to be rumbling to life. For beta testers and Windows enthusiasts, 2005 looks to be a busy year.
Which I read as, “Don't worry about having to support Longhorn in the real world until at least 2008.” That's not an inidictment of the product. Just means that I'm going to go back to working on solving problems with technologies that my customers actually use - no sense getting too excited just yet.