UPDATE: Unfortunately the D500 uses a heavy crop of the sensor to readout 4K video. More about this below.
As well as the Nikon D5, we have a surprise.
Although the Nikon D5 can only record 4K for up to 3 minutes at a time, the D500 can go for a full 30 minutes in one continuous take.
The D500 also comes in much cheaper than the larger FX pro body.