Nobody is going to go out of their way to buy it, the only installs it will get is as OEM's on new hardware.
And I bet even the OEMs will offer Windows 7 for as long as they can.
I think if users _have_ to have something different they will seriously consider OSX and Linux. One is more polished on better hardware for people who have money and want the best. The other is free for people who don't care.