Mary-Jo Foley from Microsoft Watch was trolling through the dry and as she calls it 'somewhat obscure' Microsoft lifecycle website. ;-)
She discovered something interesting. Many Microsoft experts were thinking XP Service Pack 3 would be released late 2006. In fact, it's running almost a year later than that; the latter half of 2007! You can expect W2K3 Service Pack 2 second half of this year.
Other interesting data is that Redmond quietly pushed out WinXP home support to at least 2008. Makes sense, as some people pointed out that XP Home, and most other XP OS-en, would be cut off from tech support at December 31, 2006, a potential snafu since XP's successor, Windows Vista, isn't to release until shortly before that date!
If you have some time, and do not mind pretty dry pages, there are some nuggets hidden in the Redmond lifecycle site:http://www.wservernews.com/VT1RT8/060113-Service_Packs