Microsoft announced to extend the availability of Windows XP until 2010. The original plan called for discontinuing XP this Summer.

Microsoft cites the new class of mobile personal computers commonly known as ultra-low-cost PCs, or ULCPCs as reason to extend the life-span of XP.
Microsoft has heard (and apparently listened) from partners and customers that they want Windows broadly available for this new class of devices, because they want the familiarity, compatibility and support only available on the Windows platform.

Asus with their Eee PC, landed a big hit and the low-end hardware can only run Linux or Windows XP. Vista would drive the hardware cost way to high.

I still run Windows XP on my desktop and I would not have stopped doing it this summer.
Via this Microsoft press-release.

The Asus Eee PC with XP will start shipping on April 9th in the US.