If things go to plan I'll consider upgrading around 2012.

Of course, the other major problem with Vista is the huge carbon footprint which will be left after the majority of users discard their still functioning hardware.
This will need to be disposed of in one way or another. I've heard people say "the old kit can be used by third world countries". But, how many people will dispose of their old kit in this way and what happens to the kit that is being used by the third world. Microsoft seem not to care about these issues as its products always seem to require an upgrade of one form or another and a lot of kit being discarded.
The other aspect of new operating systems that appals me is that you do all you can to make your PC faster and more efficient and MS make their OS more bloated and demanding. The outcome of this is an expensive PC with really good specifications that now runs at about the same speed as the PC that it has superceded.
I think my philosophy on MS operaing systems are "if it ain't bust don't fix it".