Mikio Tanaka (well known photographer in Japan) posted on his blog that a Japanese magazine recently interviewed Mr. Kitazawa (head of Pentax camera R&D department) who claimed that Pentax is working on a mirrorless 35mm full frame camera and is even considering a mirrorless medium format camera with the sensor used in the 645D. The magazine will be published on December 19th.
Via PentaxForum