Under glass at CES, JVC showed what they called a “Reference Exhibit” of a 4K interchangeable lens camera and sitting in the case with the camera was a Sigma Nikon F mount lens.
The camera is listed as featuring a 1.25″ 8.3 Megapixel CMOS Sensor and F mount compatible interchangeable lens mount. A 1.25″ sensor would be similar in size the sensor in a micro 4/3 camera.
The camera also features wide band loss-less audio recording with 24/96kHz sampling using LPCM compression with a bit rate of 4608kbps.
While there were no details on pricing or availability, a little internet research turned up two technical papers for what might be the sensor used in the camera.
IEEE Explore Digital Library
A 1.25-inch 60-frames/s 8.3-M-pixel digital-output CMOS image sensor
The International Image Sensor Society
Progress in 1.25-inch Digital-Output CMOS Image Sensor Developments for UDTV Applications