No one except MFDB industry, astronomers, NASA and the defense industry needs a MF sensor. For Hollywood APS C is full size, and APS C is good enough for 4k. They don't need MF sensors and MF-lenses.
The way I see it...
While RED has been quiet about it recently, they did introduce the Monstro family, which includes these future formats. The items below come from earlier announcements (and the wiki page), but Red's web site has virtually no mention of them now.
Epic 645 56x42mm 9,334 × 7,000 (9K) 65 16
Epic 617 168x56mm 28,000 × 9,334 (28K) 261 16
I don't know if they'll ever make it, but it certainly seems that any such chip would ipso facto have to support live view in real time.
That's what I was thinking of. But who knows if RED will ever get there. Clearly the staple for video is S35, with FF35 becoming useful for wide formats.