As we approach Vista's second birthday and distance ourselves from the launch of XP further, you might assume that Microsoft would have had enough time to make Vista attractive enough for people to prefer it over XP. DirectX 10 exclusivity, restricting vendors from selling XP, marketing campaigns and so much more, all towards Microsoft's end of making Vista de facto apparently aren't working as fast as they'd hope.
According to some recent estimates, by the end of this year Vista will have been deployed in 9% of businesses and still won't reach 1/3 of the market by 2010. On top of that, factoring in downgrade licenses it seems that Windows XP is still outselling Vista. That must hurt Microsoft, especially when very large vendors have mentioned they simply will not deploy Vista, waiting instead for Windows 7.
Interestingly, Windows 7 has been in the works for a while and it's been rumored more than once that it will be released next year. That's just speculation, of course, and given the dollar investment Microsoft has poured into Vista I doubt they will just sit on their hands.