To the people suggesting the K-5 is too big: You are either pigmies or just using the wrong camera.
If the K-5 were any smaller, you'd need tweezers to hold it.
I fully agree that a modular approach would be the best way to go with a new Pentax FF camera and Ricoh would probably push it too based on their current cameras. If they went mirror-less and EVF then it would be smaller and cheaper to produce for starters.
I can see that Pentax could kickstart an entirely renewed FF market due to not having
so much invested already in lenses. They could virtually start from scratch with a totally new system design and with a new set of lenses for it. That would then mean a K-Mount adapter would be on the cards.