SP3 is now planned for first half of calander year 2008:
Windows XP Home Edition SP1 SP2
August 6, 2004 SP3 for Windows XP Home Edition is currently planned for 1H CY2008. This date is preliminary.
Windows XP Professional SP1 SP2
August 6, 2004 SP3 for Windows XP Professional is currently planned for 1H CY2008. This date is preliminary.
http://www.microsoft.com/windows/lifecycle/servicepacks.mspx
