Information Week and Neowin.net are reporting that Windows XP Service
Pack 3 may be showing up at the end of this month.  OEMs and
MSDN/Technet subscribers will apparently have access on the 21st, with
release to Windows Update on the 29th.

http://www.informationweek.com/news/windows/operatingsystems/showArticle.jhtml?articleID=207200856

This is an unofficial report - we do not have confirmation from
Microsoft for this.