According to this CNet News' report, Microsoft is considering to issue another major update to Windows XP that would follow Service Pack 2, already expected later this year.

Issuing an update to XP would represent a significant shift for the software maker, which for months has insisted that it had no plans to create a separate version of Windows before Longhorn. A company executive confirmed to CNET on Thursday that Microsoft is now discussing a product internally referred to as "Windows XP Reloaded."

MS seems to be worried that the 4-5 year gap between XP's initial release and Longhorn arrival is way too much opportunity to give competitors such as Linux. If SP2 is a more security-oriented patch then a second update would most likely consist of additional and updated features currently available in the OS.