Polikarpov,
I think a lot of companies are looking to stay with XP for as long as they can, especially as the main driver is getting Office 2007 out there which XP will support.
XP SP3 is mainly aimed at getting XP ("Windows 5") & Vista ("Windows 6") systems to co-exist peacefully so that home & business users won't have the excuse against Vista to the effect it won't talk to legacy PCs with XP on them.
Personally I'm not holding my breath for Windows 7 - it is a major change for Windows and the early developer presentations that have whispered in hushed tones about the Windows 7 kernel (if you're intrested there is something useful on InfoQ, but under the guise of Windows virtualisation futures) but it's a long way from user ready.
Reading between the lines, Windows 7 is looking like an attempt to build an "all things for all men" release that could be made small enough to go on the new super-PDAs, yet big enough to cover the mega-gaming PCs. End 2009 looks very agressive for Windows 7 development to meet the necessary QA standards - I would like to be proved wrong here.
I would suggest that we keep watching MS Towers, there could be a play to use the new Windows 2008 kernel for a desktop release. Win 2008 is already starting to be packaged as we suspect Windows 7 will be, and it's not beyond the wit of man to suspect that MS might push for a desktop version (like they did with Windows 2000).