Mobile is getting RT, fyi. Apple already has it (for a few generations, at least), I think Qualcomm does as well (I'm less familiar with their stuff, because they've been behind the game forever, however the last I've read, their latest stuff has it), and things are rapidly improving.

Vulkan is the actual barrier. On Windows, DirectX does an average job at supporting it. Microsoft doesn't really innovate these days, so NVIDIA largely drives the market, and sometimes AMD pitches in.