Since my original post 7 months ago, much advancement has been made in terms of 4K.
This 65" 4K TV will soon be at a Best Buy near you:
http://www.bestbuy.com/site/Sony+-+65%22+Class+%2864-1/2%22+Diag.%29+-+LED+-+4K+Ultra+HD+TV+%282160p%29+-+120Hz+-+Smart+-+3D+-+HDTV/8652098.p?id=1218882643613&skuId=8652098&ref=06&lo c=01&ci_src=14110944&ci_sku=8652098&extensionType= {adtype}:{network}&s_kwcid=PTC!pla!{keyword}!{matc htype}!{adwords_producttargetid}!{network}!{ifmobi le:M}!{creative}&gclid=CJHJ-76ixrYCFUNgMgods1wAHA
Some camcorders and cameras have been released that have 4K video modes. The JVC GY-HMQ10 is one of them:
JVC GY-HMQ10 4K Compact Handheld Camcorder GY-HMQ10U B&H Photo
It records 4K video by splitting the image into quadrants and recording four 1920x1080 streams to
four SD cards, which are "recombined" to deliver a 4K image. Such an awkward apporach (as well as the price) reminds me of the first prosumer HD (720p) camcorder, the JVC GR-HD1, which recorded video to an "MPEG-2 Transport Stream" as no consumer HD format existed yet.
One device that can record in 4K, albeit not at full-frame rate (12 fps), is the GoPro HD 3.