Originally Posted by Matjazz 
If shake reduction was precise enough to move sensor 0.5pix in each direction it would be possible to make an actual 4x10.2mp image with four exposures or, if shake reduction was also fast enough, with a single four times longer exposure.
The sensor would have to move like this:
each step is 0.5pix long
I guess there are other technical details in the way or someone would already utilize this principle.
Benjikan, perhaps this is worth mentioning to Pentax representative next time you meet him.
I've thought of this too. The main problem I thought of was the anti-aliasing filter which has already removed almost all of the extra information above Nyquist. Now if you cold somehow have a camera mode that also moves the AA filter out of the way, then you'd really have something.
In the meantime, it's a lot technically easier to simply double the focal length, take four adjacent photos and then stitch them together. Solves the AA filter problem as well. Downside is it's only good for landscapes, but that's the only time I ever want more resolution.
Bart