So, the new Hasselblad H6D-100C has the capability to shoot RAW 4K full frame from its 53.4 x 40.0mm sensor, which is quite impressive. Not many tests around the web yet, but from what I've heard the quality is very good, although it does have a more pronounced rolling shutter than a film camera. Also, although chip is closer to 4x3, it can only record video in 16X9, so chops a bit off at the top and bottom. But saw an interview with the CEO of Hasselblad and it seems they're wanting to explore the film side more and he hinted that it will probably be able to record the full height of the sensor soon (making it theoretically possible to use Ultra Panavision 70mm lenses on it). Maybe even a very long anamorphic 35mm lens would potentially cover the full sensor.
None of the lenses are well adapted for filming of course, but you could get older Hassy glass that it would be possible to pull focus on. Be very interesting to see some more tests on it.
Interestingly, the smaller mirrorless X1D model also shoots video on the full 6x6 sensor, but unfortunately is limited to HD only.