Originally posted by monochrome
These are all interesting discussions, but there is a reality we rarely consider.
Ricoh's entire focus right now is getting as many K-mount, Q-mount and 645-mount cameras into the market as they possibly can, as soon as they possibly can. They want to increase the installed base of these three mounts across the globe so that there is a proprietary future market for lenses and accessories. That's what colored K and Q bodies is all about.
Given a limited production capacity (at some point production capacity is always limited; at that point a new plant must be built), which of the existing Pentax or Ricoh products or mounts would you discontinue to make room for the new, shorter-register K-mount, and how would you alter the long term business plan for increasing the installed based of (whichever) mount was carried on the discontinued product? Don't forget, lenses are where the profit is, so which lenses would you discontinue - or which planned new introductions would you make in the shorter register distance instead?.
Pentax is committed to K-mount (at the 45.46mm register distance), Q and 645. Q is their short register distance, mirrorless camera line, which they intend to develop into a Q System over time. They view Q as their real growth line.
Those are good questions. Without knowing the resources available and production costs I can't give a full answer. But some aspects of a potential short-register mount can make some of the choices easier.
A camera with such a mount, but with the adapter fitted, (perhaps even built in and extendable), is
at that time a "normal" K-mount camera. It might even be a useful camera to develop and sell
even if initially it is only usable in full K-mount mode. It would look a bit like current K-mount cameras, but the body would be thinner and it would have a sticking-out lens-mount. (I should say "an even thinner body with an even more sticking-out lens mount" - cameras are already built that way!)
The lenses that would be released for the shorter registration would be those where there was a specific technical or sales advantage. Wide-angle lenses are one possibility, within the limits of catering for the edges & corners of the sensor. Lighter-weight zooms may be another. It wouldn't be the first time lenses were released that didn't work on old cameras - except for those willing to use MF, SDM-only lenses (I have 2 of them) won't work on some older cameras. It is more important that old lenses work with new cameras than that old cameras work with new lenses.
(I'm building up a comprehensive Q system, and I'm glad that Ricoh/Pentax are talking it seriously. I'm worried that they may not be talking the K system so seriously, because I'm not switching from K to Q, but rather intending to have separate systems for very different purposes and occasions).