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.