Originally posted by Adam Leave 4K video out and I think they could definitely do it,
Pentax supporting 4K will have a lot to do with whether the image processing chipsets they use also offer that support. The current '7th generation' Fujitsu Milbeaut chip that powers the K-3 and 645Z doesn't do 4K video, so to support 4K Ricoh will need to either solder on some additional chips onto the K-3 mainboard, at least, or find a new imaging engine chip entirely for the FF. Thus 4K support may make engineering a Ricoh FF more complicated and expensive.
But then again, the '8th generation' Milbeaut chip is due about now, since the '7th generation' Milbeaut is over a year old. Maybe a new chip will support 4K, and Pentax could then quickly, easily and cheaply offer 4K video just by using that upgraded chip.
If you see any press releases from Fujitsu in the next few months about chips that support 4K, then that will increase the probability that a Pentax FF (and other new Pentaxes) will also be able to offer 4K video.