So what happens to the Mobile aspects of UWP apps once WoA comes out??

WoA still has lots that we do not know about, if I get somethings correctly it will be using the same apps on PC since basically it's full Windows 10. Well that means developers won't have to worry about checking a mobile box to enable their apps for current W10M. Develop once and it runs on all PCs and WoA devices.

So that leads me to this question, without W10M support (not now but one day) and with the full unleash and focus on WoA by both Microsoft and developers, will this check boxing to enable UWP apps run on mobile be redundant? Considering developers will now develop once for Windows 10 with no mobile scaling in mind. Developing once for Windows 10 with CShell handling scaling on smaller devices like mobile. And if that be the case, then one day UWP apps won't even run on our current devices......since well, CShell won't even come to our current devices and also developer didn't check the mobile box whilst developing the app.

Maybe I'm lost with this whole explanation of UWP and WoA and hope someone can clarify things up, thanks.