Seems like in order for "Windows 10" to succeed as a whole (PC, tablet, phone, Xbox, etc.) there needs to be a tectonic shift away from traditional Win32 apps to Microsoft's "Windows Apps" (aka Universal Apps) model.
Is this a realistic idea and would it ever happen?
The reason I ask is that there are various apps that run traditional Win32 (iTunes, Chrome, etc.) - what is the motivation to these companies to transition to "Windows apps" versus Win32, beyond reach to additional devices? Is it better in any way?
Well, more and more Windows apps seem to appear and some of them are actually pretty good.
Will they replace Win32 Programs? Not in the next decade in my opinion...What about later? Yes. Slowly, but yes.
I believe that it's easier to make a Windows app. especially for new, excited and inexperienced programmers, so they would choose to make Windows apps. However, some famous Win32 Programs like WinRAR and Photoshop will probably never become Windows apps (WinRAR might actually become, since it's a small program, but rewriting Photoshop...no).
But it's not just that. Making Windows apps allows you to easily provide new updates to users and easily receive feedback, while it makes downloading applications easier and safer (one place to find everything, one place where everything is safe).
So, considering all that I would say that Windows apps will get much more popular in the next few years. More and more well made Windows apps will make their their appearance, but it's going to take a lot of time to replace Win32 programs, if that ever happens.
And don't forget: The only way for Windows apps to succeed is for Windows 10 to succeed. It must become the new Windows 7 and Windows 10 should also get better sales than WP8.1 sales.
(Sorry if some of the stuff I wrote doesn't make much sense. English is not my first language and I am in a hurry right now, so I can't check for any errors!)