Lol. Skillets. But seriously, I doubt this happens. Even if 50% of the country owns an Apple product, far more than that own any kind of computer. Don't count windows out.
It's not going to be an overnight thing, for sure. But the erosion is occurring, absolutely.
I mean, as a maker of software, I would want my product to run on as many platforms as possible to maximize my revenue opportunities. I would always look toward open solutions rather than proprietary ones, and now with the mobile/tablet market set to outpace the PC market, there are far more customers there... Windows isn't a player in this new market.
I think the tide is definitely turning. Not that people will stop creating apps for Windows any time soon, but they will build them in a way that assures deployment on iOS (Mac OS X) as well. No more proprietary stuff.