The problem is: the platform owners (Apple and Google) have absolutely no incentive to make this see the day of light. They make money selling apps, and want to bind developers to their platform.
In some respects I think they've already paved the way. An adapter could be created to target canvas or WebGL. As for APIs like file system access, I don't think there's anything wrong with the JS web APIs as they exist today. I'd love to see Apple actually push ahead with the implementation of more of these APIs, as well as PWAs, etc. but I know it's not at all in their interest.
