The 5D MK III sensor is only a tiny amount larger than the 5D MK II, so the additional resolution is not going to be significant.
The improvements are the faster readout, better on chip NR, and the improved high ISO. We don't know what features might be removed in a low cost camera with this sensor, but if it has the same image and High ISO performance, and accurate autofocus, I'd be happy to upgrade my 5D MK III.
If it did not have the lcd in the viewfinder, that would be a improvement.