Microsoft is playing their cards right
The [unconfirmed] news about Windows Phone users not getting an Apollo update is [maybe] because of the kernel being based to Windows 8. If this happens, it would be much easier for Windows to garner the attention of developers to create apps for them especially if WP8 and Windows 8 are already released. If OEMs introduce Windows 8 to their products and even offer upgrades to their previous products like what they did in Windows 7, Windows 8 would definitely be the main OS of PC users.
As you could see, Microsoft is trying to "connect" the three OS, Win8, WinRT and WP8. Developers would definitely be creating apps for Windows 8 because of its large user base, and those apps could also be used in WinRT (Windows 8 ARM devices), and with that, they could easily create apps for WP8.
Basically, what I'm trying to say is that:
More users of Windows 8 = More apps for Win8 and WinRT = More apps for WP8 = More users for WP8 and WinRT
And even though existing users won't be receiving the Apollo update, starting Apollo, Microsoft will win the PC, Tablet and Smartphone industry because of their smart move for the Metro UI for all devices.
And of course, Apple does have an incredible user base of Tablets and Phones but I'm pretty sure Microsoft can reach or even have greater user base in the future.
I would also like to add my suggestion for Windows 8, Microsoft could have Metro-styled the Desktop and completely erase the Aero UI so it could have more uniformity.