UHD needs to be more than extra pixels, sure, but will the manufacturers and content providers stop being boneheads and allow it to be so?
Lossless, 24 bit object-oriented sound as good or better than the theaters? 10 bit or 12 bit video at 4:2:2 or 4:4:4? A much wider color gamut? Whole frame rate encoding for film content and not just video? More variety of native frame rates, so no frame rate conversion is necessary for any region or zone (24, 25, 30, 48, 50, 60, 120)? Etc. Etc. Etc.
They could go all out, but what usually kills the quality is the type and severity of the video compression utilized. It really must be visually transparent to the master.