I also like to ask the question, what is wrong with the sensors from canon? It is true, that Sony's (and Nikon's) are better at the moment, but does it really matter? Up until a year ago, the EOS 5D II was the non plus ultra for outdoorphotographers. It was praised for its high IQ, now the mkIII is even better, so what should be wrong about it.
Sure, a better sensor always gives you more possibilities, but is it the limiting factor; and what is the limiting factor of the sensor? Sony (Nikon) sensors have the higher dynamic range at low ISO and the better color sensitivity, while Canon still performs better at high ISO. If you just take the DxOMark score as a measurement, then Sony (Nikon) is far better than Canon; but these marks say about the quality of a camera about as much as a 0-100 time for a car.
To be honest, I expected a bigger step in IQ from the 5d markII to the 5d markIII, but it was still an improvement from an already very high level.
So should Canon keep making its own sensors? definitly yes.