That kind of reminds me of the Stockholm syndrome a bit. Vista was very disappointing, because users expected something good after XP, and it wasn't. By the time Windows 7 showed up, users were even more tired of XP than they were when Vista launched, and they couldn't wait for a "decent" alternative. After the low standard that Vista set, they were happy that Windows 7 was at least as good as XP or better.
But now people are not tired of Windows 7, and some just upgraded to it a year or two ago. Add that to the fact that it makes the desktop experience very confusing, and I don't see Windows 8 being very successful.