Windows 7 might only have two years of newness left.
After Windows 7, the expected next evolution will be Windows 8. While Microsoft has confirmed that it is working on the next-generation of Windows, it hasn't said anything about release date. Speculation put it into sometime in 2012, but Redmond isn't confirming.
Interestingly enough, the Microsoft blog in the Netherlands had a rather interesting post talking about the upcoming release schedule of Microsoft products. Windows8beta.com ran it through a translator and this is what it read:
The phasing out of Windows XP, Microsoft is nearing completion. In July 2010, the support for Windows XP with Service Pack 2 stops. Today Microsoft will stop selling Windows XP to PC manufacturers and the aftermarket sales of Windows Vista. For Windows 7, Microsoft Service Pack 1. This service pack is still in the testing phase and is expected in the first half of next year available. The first update of Windows 7 is the new version of Windows Live Essentials (explore.live.com) became available in mid-June. Furthermore, Microsoft is of course the next version of Windows. But it will take about two years before "Windows 8 ‘on the market. The latest news about Windows is available at www.windows.nl / blog.
So according to that, if you're waiting for Windows 8 before making the move from your Windows XP install, you'll be waiting "about two years" before it'll be on the market.
Predictably, Microsoft took down the blog post and changed it to mention only Windows 7 SP1 and the new Windows Live Essentials that was released during the summer.