Dell's just announced a 4K 32" monitor at SIGGRAPH
The new 4K device with "a screen as big as your imagination" has a resolution of 3,840 x 2,160 and uses IGZO technology and has a 1.07 billion colour wide gamut.
It's targeted at profesionals, with features like the Dell "UltraSharp Colour Calibration solution" that includes LUT access.
No word on price yet. Expect availability in Q4 2013.
Likely to be expensive
This is likely to be pretty expensive compared to conventional monitors, but we may be pleasantly surprised. In any case, prices for 4K monitors are likely to fall quickly as production of 4K panels ramps up.
With a single HDMI 1.4 connector, framerates are likely to max out at 30fps.
See our article on HDMI 1.4 vs 4K framerates here. http://www.redsharknews.com/technology/item/682-is-hdmi-ok-for-4k