4k is refereed to cinematic camera resolutions, 4096 pixels wide, and shot at 24fps. It is a standard by Digital Cinema Initiatives. Tons of content shot at this resolution, the work I do we have been shooting digitally in 4k ad 6k since 2009. Also uses CIE XYZ colour space, UHDTV will be standard illuminant.
You all miss my point, the current TVs will not be compatible with UHDTV. Biggest difference apart from rec202 is having to support 100 and 120Hz, all progressive.
As for tests, BBC in the UK plan to launch UHDTV1 service over DVB-T2 in 2016, this has enough bandwidth to support this format. UHDTV2 has some more hurdles.
Only a handful of monitors support UHDTV, they are mostly professional grade 1 panels, and in 4:3 (so we can have other data above and below the image). Current '4k' TVs you could say are UHDTV 0, it is what we call them. We keep 4k different to UHDTV so we do not get confused.