The 5D III (or 5Ds) should be the studio/landscape cam. That was the 5D line designed for. An AF with less then 19 points is logical.
A 5D X should be the sportier version: a 22-26 mpx, better AF (19 cross points or 1Ds3 AF dunno) and better ISO.
I worte it many times, even if they put 61 points AF in this body from the 1D X they can put big limitations in other aspects, and there you have two roads for both lines. Think at the buffer, or fps, or the advanced menu for the AF. They can enable limits in every aspect.
Canon's strategy with 3 FF bodies it's flexible than Nikon's. Nikon doesn't have a D4 sensor in a D800 body.