For those apps to exist, they first have to get Windows phones and tablets into the hands of users. Developers aren't going to make the effort if nobody is using the platform. That's one of the reasons for the push for inexpensive Windows tablets.
Unless you use the Metro apps, the Windows 10 technical preview already does look mostly like Windows 7. (One obvious change: the addition of tiles to the Start menu; they coexist with the traditional menu. And there are cosmetic differences in the login screen and the screen you get when you type Control-Alt-Delete. But I don't think any of those changes will be deal breakers for fans of Windows 7 or even Windows XP.) On a desktop or laptop system with no touchscreen there is no compelling reason to use the Metro apps; they are less convenient than conventional applications if you are using a keyboard and mouse. The only notable exception is PC Settings because it's the only way to create a new user; unlike Windows 7 but like Windows 8, the User Accounts piece of Control Panel lacks that capability. But Metro apps are more tablet-friendly than standard desktop applications, so Microsoft is surely hoping that the adoption of Windows tablets will lead to the creation of more Metro apps, which will in turn help drive adoption of Windows phones.
The only certain thing: Windows RT is dead. Now that inexpensive tablets that run full Windows are available, there is no reason to live with the compromises of RT. If Microsoft chooses to make a Surface 3 or a Surface Mini it should run full Windows. They may stay out of that segment altogether to avoid channel conflict with other companies making Windows tablets, and just continue the premium Surface Pro line.