@love2scoot: It doesn't matter what the standard theoretically supports if there is no real hardware that can handle it.
I agree with you. One thing specifically that sets the 7970 (the video card used in the CES booth display) apart from other video cards is this very ability to push 4k through a single HDMI or DisplayPort 1.2 connection. This is one of the big features that AMD is pushing to help differentiate this card from other cards on the market: it fully supports the throughput specified in the standard.
The irony is that the display they had attached to this video card required two cables.
The good news is that production of the 7970 (as well as the Sony BDP-S790) shows that the faster silicon is finally becoming available in production level volumes, which is good news for us all.