If Pentax don't go with micro43 (but I think they should, and make cameras that blow Panasonic & Olympus out of the water!!!), they STILL have to do something "innovative", which is what was being talked about a few months back.
This is pretty much the setup for any current mirrorless camera:
It still has a shutter, which takes up a fair bit of "free space" vacated by the mirrorbox. The lens still takes up a fair bit of space out in front of the camera, rendering it as not REALLY pocketable.
However, suppose Pentax produce a shutterless camera (this is on the cards as Kodak has a sensor that can support this, for example), then this frees up space inside the camera.
So now, interchangeable lenses can be designed to retract into the body when powered off, but extend to the active mode. It would mean that it WOULD be pocketable, would be innovative and would jump the others!!