Judging from Windows Store/UWP/etc acceptance, it doesn't really seem much of a future.
> they would need to rewrite the applications from scratch
Nah, this is never going to happen with Windows. The worst you can expect is to not get any new features, but even with base Win32 you have enough functionality to build on top of it anything you want (and/or use 3rd party libraries that bring that functionality).
It might be some future for niche/specific uses, but i'm certain the current model of downloading an installer for applications and games or having a (non-sandboxed) downloader like Steam, Galaxy, Origin, EGS, etc will remain the most common by far.
Unless Microsoft tries to force that, but they'll certainly face a lot of resistance and with their apparent coupling of Windows Store with the sandboxing model they could face antitrust issues that would dwarf the IE vs Netscape case of the 90s as there are way more money and businesses involved nowadays (and of course Valve/Steam waving their Linux support all over MS' face :-P - that story has calmed down now but consider how many companies flared up just because of the idea that MS could potentially lock down Windows with Win8).
Yes, but it isn't orthogonal to 3rd party stores in that you need to escape it for them to work. And really the same applies with a lot of other application types too.
