Panasonic has a Lumix GH-4 4K camera on display under glass, but without pricing or availability. Perhaps the official announcement will come at Photokina in February. Sony, Panasonic and others are announcing “action cameras” to compete with GoPro Hero cameras.
I think 4K capture is useful and important but am not enthusiastic for the 4K TV market in the near future. Most consumers do not replace expensive TVs frequently and most just recently upgraded to HDTV.