Microsoft shared information with this site WinInformant as to its future Service Pack for Windows XP.
The main innovations in this service pack include:
Tablet PC This feature will enable OS operation on the portable screen-PCs. Earlier MS planned to release a separate OS version for it.
Mira Somewhat vague-device support that would allow you controlling your PCs from a distance. Devices like handheld and touchscreen compatible with XP that would allow using it as remote control for your PC.
Freestyle This should let you turn your PC into a digital entertainment center. A load of features to turn your PC into a powerful multimedia station.