Thanks for the explanation. However, I wonder if the physical infrastructure needed to perform a global shutter wouldn't have implications for still photography. A rolling shutter seems to be the necessary result of having slower processers/read rates (I could be wrong). To pull off a global shutter I would expect you would need faster or more A/D processors and faster read rates. I wonder if such hardware could benefit still photography in terms of fps and possibly (elephant in the room) noise.
Or you do it old school, with secondary buckets. Give each sensel the capability to put its current charge in a non photosensitve area. Then you have all the time you want to sample. Another option would involve a Kerr- or Pockels-effect based shutter.
But Canon wants more readouts anyway - DPPD-AF makes you want to potentially read the whole sensor*2 at the refresh rate of the current PDAF-sensors (and prcess that data).
Well, Sonys high end compact can read,process and compress to video 60 iirc 20MP-images per second, a similar core in a dual configuration could do quite a lot...