no video cards have HDMI 2.0 yet but both nvidia and AMD latest gen will do 4k with dual HDMI (yeah thats exactly what it sounds like) or displayport/dvi-d. I don't think any 4k TVs though allow you to output 4k @ 60hz or higher over 2 HDMI cables, they only do 4k @ 30hz over one. HDMI 2.0 is being finalized and should be mass produced next year.
I saw the Seiko 4k at Frys here, we hooked it up to a laptop and it was not that great. Decent enough text size and DPI but pretty bad input lag at 4k (@ 30hz), we could kinda run it at 1080p @ 120hz but saw a lot of ghosting and flickering problems.
the gSync stuff is going to be heaven, everything I've seen of it make them look even better than the old school gigantor CRTs with no input lag and snap refreshing, seriously wanna wait for those. Until then, the $350-400 27" 120hz 2560x1440 eBay DVI-D monitors are a dream, I have two and they look amazing just dunno what the quality is like, but for the $350 I paid each (5 day free shipping from korea) they will hold me long enough until gSync is easily available.