The thing is, if you step back and look at it, the operating systems that have survived, were better than the previous ones.
There's a reason why no one was ever forced to buy Windows Me. It sucked the big one, and never got the installed base. If Vista is as crappy as many make it out to be, people will stick with XP. The primary reason behind us eventually having to use XP is because eventually, XP became more widespread than 9x.
When I finally switched to XP, I found it superior to my 98 SE in almost every way (what's that, I don't need to restart for changing my IP? What a novel concept!!!). And I don't find myself feeling I need to reformat every year.
If Vista sucks, people won't buy it. MS wasn't successful in trying to get the OEM manufacturers to make Windows Me the home user operating system (I found it quite funny that you could buy Win 98 SE long after wholesale distributors quit selling Me). Microsoft is a big company, but I don't think even they have the capability to force a crappy Vista down our throats while XP is around. If Vista doesn't have good sales, software companies will not make software for it, as it wouldn't be economically viable to do so.
Heck, you can't even get people to adopt a superior operating system if it doesn't have the software support. Microsoft needs to get the software support for Vista for Vista to be successful. Otherwise, Vista will tank. If no one buys it (because it's too restrictive or whatever), then no one is going to bother developing for it.