I may buy new computers for the office right before the Vista launch. We don't strictly need them but I'd really like to avoid converting for as long as possible. Despite all the grief it gets, a properly set up XP system is really quite good and I'd much rather see MS engineering effort going into releasing XP updates than into a whole new OS, even though it won't happen because there's no money in it for them. I'd almost rather them release "XP2" and charge for it; I'd rather pay for that than pay the same amount for Vista.
There is no not really much (additional) money in it for them with the upgrade either. As stated in the article, a very minor proportion of sales are something consumers actually go out and buy. They make their money off the pre-loaded software you find on almost every PC (whether you want it or not). They'd be making money even if they never did anything more than issue service packs for XP-eternity.
This "upgrade" is largely an ego thing on MS's part, and is partly in reaction to OSX.