Current display technology, using HDMI 1.4, can only do 4K at 30fps. This has rather limited the adoption of 4K screens since there has been no way to get high frame rate content all the way to the display – and of course there’s no way to do 4K in 3D. (This is beside a point that there’s precious little source 4K content and the solutions from e.g. Sony have been whimperingly pathetic, effectively equivalent to attaching a large USB stick full of preloaded movies to your $10,000 television.)