[K0SM0S]

Could work as a preprocessor on the dev side for quickly outputting each native API code from a more general form, probably designed as a superset above SPIR-V (bound to be a bit more verbose than pure native code, but even a 100% larger project is better than 2+ discrete ones). Maybe even JIT if they can essentially extend LLVM (or at least generate direct hooks through the preproc).

I don't see much 'impossible' on the tech front, however politically... it's just my intuition but somehow I see Microsoft and Apple not cooperating much beyond WebGL efforts, and actually baking progress into their own proprietary APIs/platforms.

The matter of the fact is that as of today it's still profitable to develop 3D applications even under the restrictions posed by proprietary APIs, and OpenGL/Vulkan are still optionally usable too (though generally worse performing on Windows or Mac, notably because there's no efforts by MS or Apple to help). So there's really not much incentive for opened platforms. Essentially users are absorbing the costs (more money and/or less features, e.g. cross-platform game which sunk costs in porting/licenses rather than content), but so far don't complain much about it (probably because there's no comparison to be made in the real-world with opened platforms since none of the commercially successful OS is truly open at the consumer level).

As so often, nice spirit by Khronos, unfortunately they're so lonely on that road, surrounded by giants with conflicting interests and much wider preoccupations (read: emphasis on building an ecosystem + verticality of control). See Surface lineups, or even Google, now making Pixels. Actually the latter is a prime candidate to further Khronos' goals, I wonder what the 3D API landscape will look like on their alleged x86 efforts.