The second paragraph is the key to me (I'm assuming the first paragraph to be true, that it's hard to tell HD from 4K when only resolution is changed). I'm not so concerned with higher frame rates, but better color space, bit depth, and dynamic range are areas that need some iteration. I would be more than happy with 24fps (or 30) at HD with better color, and dynamic range than the current craze of bigger resolutions that we can't actually deliver. The press to 4K seems like little more than marketing at this point to me (save for the rare benefit that you can (1) show it in its original resolution on a screen that benefits from it, (2) do pan & scan in post for mastering to HD).
For why 4K still doesn't matter in your home, see here.