Unfortunately, we may have an answer, at least for now, about "4k" media... the BDA has plainly stated they think a BD50 is large enough for a full 3840x2160p movie using MPEG-5. That means a standard 8 bit, 4:2:0 consumer video stream that we've all come to loathe, and extremely high compression. I don't see how that would hold up well on the extra large flat panels and projectors they now want to push. It's clear that with 4k, manufacturers are going for the "BIGGER IS BETTER" mindset. I'd also assume that projectors and screens will be advertised more heavily than they are now in order to "bring the big screen movie theater experience home in glorious 4k."
Now, if they moved to multi-layered BD's (BD100 or BD200 GB discs) or a holographic type storage disc and increased the bitrate, it would be possible to not only lessen the compression ratio, but easily allow for higher progressive frame rates, more professional color gamuts and dynamic range, and full 4k 3D... and it would look stunning and without noticeable artifacting.
Pressure needs to be put on these guys before a 4k home video standard is set in stone.