Curently the majorty of pc users are either using XP or 98. If we thing of the life span of the average users computer of being 3-4 years, in this scinario every user will be used to seeing a new version of windows every time they purchase a new machine. Perhaps simply going into a computer store and seeing a new OS is enough to convince the purchaser than now is the time to purchase. With the next windows OS scheduled for release perhaps as late as 2006 does this leave enough of a gap in the market for alternatives to swoop in?
It might be enough to perhaps make a user look more towards an Apple than a PC. Imagine a user bought a new computer 2 years agow just after XP came into circulation. Next year they go to have a look around. To a lot of users the operating system is "their computer" why buy something you already have. They then see something different on another display. Imac Emac etc...
Could get interetsing.