http://www.extremetech.com/extreme/198223-investigating-the-gtx-970-does-nvidias-penultimate-gpu-have-a-memory-problem/2 among other sites show less than 30 FPS on games. This would really upset a gamer.

2. HDMI cables. Hooey. CNET covers this at:
http://www.cnet.com/news/4k-hdmi-cables-are-nonsense/

3. http://www.cnet.com/news/hands-on-with-nvidias-new-titan-x-graphics-cards/
Notice the 980 turning in 36 FPS with a trio of 980's?

You may want to consider how much it costs to drive 4K at reasonable frame rates today.
Bob