An interesting recent article on DCWatch magazine's website today about
using the K-5 II with some classic older Pentax lenses [Google translate], including the A85 1.4, A*200 2.8 etc, as well as some discussion of the history of the K-mount, going back to the days of co-operation with Zeiss.
The article concludes with an interesting observation:
"Pentax has stated the development of a 35mm full size machine, the market for Pentax lens that covers the full size will stand up once it is released. ZK mount lens group of COSINA that are sold to the end, and regrettably genuine A lens, should not be long before it is to have a strong presence."
I think that means the author is forecasting that once Pentax releases a digital FF, expect the price of older FF glass to go through the roof.