Drives that can play UHD disks probably already exist. That isn't really the problem. The problem is no software that can decode UHD disk DRM is being sold yet, and there are no announced plans to sell it in the future.
It seems easy to guess why- everytime Blu Ray or DVD DRM got hacked it was because a Windows app was exploited to give up its secrets. No Windows applications means no DRM hole, and so far UHD disks have not been cracked so it seems that theory is somewhat valid.
HTPCs are dying across the board- only a small subset of computers can get 4K Netflix, UHD disks are unplayable, and Cablecard support is dying. It is sad times for the segment.