That model is failing them pretty badly everywhere except the business world - but even there, it's starting to falter. How many businesses do you know that jump on every new Windows release rather than riding out the versions they already have, because they're cheaper and are a known, well-used system that's not likely to suddenly change and introduce new problems for IT.
The "other businesses use MS Word so I have to use MS Word to interoperate with their documents/presentations/etc." lock-in is the strongest thing they have going for them, but even then, they're playing a dangerous game with that. You can use a pretty good online document editor/spreadsheet editor/presentation maker that works on any internet-connected computer and doesn't lock you into MS formats. Apple computers are massively popular with people in colleges and universities. It's not a good place for them to be.
But Microsoft HAS launched their version of the App Store now, with clauses that give them a hefty cut of every sale, same as Apple. They've clearly seen the success Apple has had there and want a piece of that pie. It's semi-optional right now in Windows 8... desktop apps can be downloaded and installed as per usual, but any "Metro" (or whatever they call it now) apps can only be purchased through the windows store. I see that as the direction they're going to push. The split desktop/metro interface thing is incredibly counterintuitive and stands in stark contrast to a lot of the design ideals and aesthetics on the "Metro" side of things - I see that as a stopgap measure so people can still use their existing software and they don't suffer a huge backlash when everything suddenly stops working. Likewise, I see them heavily pushing the "Metro" apps and eventually transitioning to them (and the windows store) exclusively.
They've invested a lot of developer time, money, and resources into building a whole new set of core software libraries, infrastructure for the windows store, and a whole new class of devices based on it (surface) - they wouldn't do that for something they thought would be a one-release sidenote and then abandon it all to go back to the old win API and classic desktop.
If all else fails, use fire.