The majority of people wont rush out and buy vista.
For the 6 months after release I reckon the majority of machines running vista will be new builds with it already installed.
A lot of machines wont be capable of running it without major upgrades. And unlike the move from win3.1 to win95, I cant see people rushing out to buy new graphics cards. As most people who cant run vista due to the graphics cards will be using AGP. As we all know AGP is dead. So its a new mobo time. Oh, and if your using an old socket A chip, a new CPU. Then u need new memory... Wait a minute.... U need a new computer. One with it preinstalled....
I wont go into my reasons for not LIKING vista, but I think the above is an objective and reasonable outlook for VISTA. I think MS have waited too long before releasing this OS that the chances of people upgrading the odd thing on their computer has passed by. Were talking new RAM, new CPU sockets, new Graphics ports, etc...
However, if your on the lookout for a bargain second PC, wait until about 3-4 months after vista is launched.... It will be cuthroat in the 2nd hand department, I do think there will be some VERY good bargains...
Oh, and one final thing. Remember im talking about the majority of people, the moms and dads who goto retail parks to buy their computer needs, and not come on websites like this.... Were the minority... Those in the know, and im sure that a LOT of people on these forums will be running vista in one form or another once it released....