I think you missed the point I was trying to make. When SACD came along, people chose convenience over quality and later made iTunes the worlds biggest record store.
With Bluray being as good as it is, 4K will only be benefitial to those with very large screens. Granted, I have that myself, and I gather most of you guys do to, hanging out on this forum. But most people dont, and wont benefit much or at all from 4K. So why would they bother with another physical format, when they can remain perfectly happy with 1080p or even 720p directly into their SmartTV NetFlix app?
Even if they need another device, download is still more convenient. Where I live (Oslo, Norway), Videostores are so rare, obtaining physical discs is getting increasingly difficult. I find it hard to believe people will go out of their way to obtain the 4K version of any movie when they can just turn on their 99$ Apple TV and stream it in 1080p instead. Unless they are one of the few with a 100" screen.
Introducing a new physical format at this point is something I think will be very difficult. Sonys "download to a box" sollution could have been a great alternative had it not been limited to use with their TVs.