The 1Dx gives clear signal how Canon cameras will be like in the future. It also indicates that Canon is listening to users that the pixel war is over, and most users are happy with 18MP, but want high ISO performance instead. So here is my predictions:
18MP, 5-6 fps (probably 5 fps), better AF system than it has now. In this way, the 5D3 will be the new king in ISO performance when it come out. The smaller pixel count also forces those who actually need more pixels to buy the more expensive 1Ds4 (do not feel sorry for those people. They are professionals and make enough more to justify the cost. See more below).
It will have 36MP, 6 fps, 1Dx AF system.
Why I believe its pixel count would increase?
1. To compete with medium frame cameras. So those who were forced away from 5D3 to 1Ds4 are actually saving money, LOL.
2. The new generation of Canon lenses are all sharper than the last generation, with a 50% increase in price. For example, 200mm f/2.8 IS or 500mm f/4 IS. A camera with more pixels can better take advantage of the added sharpness.
One thing I am not sure is if the 1D series with 1.3 crop factor will continue to exist or not.