Noise in next generation Canon 7D should match Nikon D800

The signal-to-noise ratio should depend on pixel size (pixel pitch).  In the 18 megapixel sensors on the Canon 7D and the 60D, the pixels are almost as large as the pixels in the 36 megapixel full frame sensor on the Nikon D800.  Should we not expect a similar signal-to-noise ratio in the next generation of APS-C sensors from Canon even if that means using SONY sensors?
C Sidney