The video function in the DSLR or mirrorless cameras seems to be more or less just about the codec and data transfer, as the raw video signal has always been there which enables the live view.
The remaining essential problem should be the rolling shutter effect. Even if the image quality like the high ISO performance and the reslution have been improved, rolling shutter effect should be a big wet blanket. Sony Alpha 9 with amazing continuous shooting mode is notorious in this respect.
The data read out speed of the new Fuji sensor is 17ms while that of the sensor in Panasonic GH5 is 13ms. The read out time of Fuji sensor is a big improvement but only "for an APS-C" sensor.
Unless the global shutter or a similar technology is established, it would be difficult to make a dedicated video camera with the current, relatively large sensors available for DSLR/mirrorless.
