There already is a patent for adding more pins to the EF mount, but it looks like its for video purposes:
An in-lens leaf shutter in a couple of high end lenses would be very nice. At smaller apertures it should be possible to get flash sync at the fastest shutter speed the shutter allows, and at larger apertures it should still be much faster than at 1/250th of a sec - probably around 1/1000th of a sec.
However, leaf shutters do add an additional type of vignetting at faster shutter speeds - when they're operating at their absolute maximum speed, the centre of the frame is open from the start of the exposure right the way through to the end - but go to half way out on the sensor, and 1/4 of the time into the exposure the sensor finally gets light hitting it, and 3/4 of the way through, it closes again - so at that part of the sensor, there's only 50% of the light. At the extreme corners, the aperture only opens momentarily, so close to 0% of the light hits it. Therefore it would be nice if there was an option to select which of the two shutters is used if such a lens is mounted - leaf shutter for flash work, and focal plane shutter for non-flash work.
I would assume that would be easy to correct in post or even in camera.