They'd have to be really, really careful going down that path, though. Microsoft's biggest advantage in the OS landscape, aside from preinstallation deals, has long been the broad range of established software that is exclusive to Windows. It's tough to migrate your business to Apple laptops or Linux servers or tablets in the mobile workforce if several key applications that 1,000 of your staff have been using every working day for a decade don't run on those other platforms. It's a closed loop for software developers as well, because as long as your customers are almost all on Windows, there's little benefit to developing for other platforms concurrently.
With so many business applications now offering web-based access, that exclusivity has already been eroded, and that process shows no sign of slowing down. If Microsoft were to nerf the long-established Windows APIs that "heavyweight" software like graphics and CAD packages rely on, that would force the redevelopment issue for those software developers, and I'm not sure Microsoft would like the long term results. They might wind up with exclusive control of the main delivery channel on Windows, but that only matters if the developers and users are still on Windows at all. With gaming in particular, we've seen in the past that one or two smash hits can be all it takes to establish a new platform, whether it's one of the consoles or mobile or just puzzle games via Facebook. With the resources available to Steam, that has to be a scary prospect for Microsoft.
> "The risk here is that, if Microsoft convinces everybody to use UWP, then they phase out Win32 apps. If they can succeed in doing that then it’s a small leap to forcing all apps and games to be distributed through the Windows Store. Once we reach that point, the PC has become a closed platform. It won’t be that one day they flip a switch that will break your Steam library – what they’re trying to do is a series of sneaky manoeuvres. They make it more and more inconvenient to use the old apps, and, simultaneously, they try to become the only source for the new ones."
I like windows today but I have no real loyalty. I would have no issues with leaving it for Linux the day it's too locked down.
Seems far-fetched but I can see Microsoft slowly deprecating Win32. It would be similar to when Apple deprecated Carbon, only slower: they'll stop adding new features, they'll tell developers to avoid it for any new development, etc. Won't happen overnight though as they're too much legacy software out there, but it could happen in the span of several years, a decade or so. Right now what I'm saying is fiction but it's a possibility any store developer like Valve and customers too should have in mind.