Unfortunately, Microsoft is releasing few details about the service pack. According to an e-mail from a Microsoft spokesperson, "We're currently planning to deliver SP3 for Windows XP in the first half of CY2008. This date is preliminary, and we don't have any more details to share at this time."
Several questions to Microsoft were left unanswered, including any timeline for beta releases, either public or private; new features, fixes or upgrades; and whether SP3 is a response to XP's continued market strength.
News source: Redmond Channel Partner Online