I read the patent last night. I don't think that they ever promised that it would result in high pixel counts and moderately inexpensive production. All that they have stated is that this is novel. ( I don't have a copy in front of me, so I might be wrong).
It makes very tedious reading and there seems to be a lot of repitition, no doubt for legal reasons, but there's an implication
in the extract I quoted a couple of posts ago that the new invention by Nikon does not
suffer from the disadvantages of the existing 3-CCD/prism method which, as they mention, is large, complex and expensive.
Both systems need 3 'light receiving surfaces' for each pixel, whether you call them photodiodes or CCDs, but one method uses dichroic prisms instead of dichroic mirrors. Both systems seem very complex to me and it's difficult to imagine how so much engineering could be fitted into a 5 micron wide space.
But as you imply, before the patent expires in 2023, nanotechnology might have progressed to the point where such an idea can be implemented economically on relatively small, high pixel count sensors.