There is also a patent granted to Ricoh a while back "where lenses were split into two parts - basically the lens elements in one and the iris part in another. The iris part was then built on the camera body as a fixed part. The interchangeable bit was only the lens and presumably the focus mechanism only" (source).
Two weeks ago, during the Paris's Photography Show, Ricoh representative said (source): "We are going to issue a small interchangeable lens system instead. It will have a APS-C sized type sensor.... It will be as small as the GX."