I have received quite a lot of email in the last twenty fours hours asking about the performance increase in the new Canon EOS-1DX MKII in terms of both Auto Focus and ISO. I can tell you from demonstration only that the ISO performance in the new EOS-1DX MKII is at least 3-stops better than the current 1DX (and thats being conservative). ISO 10,000 files are effectively clean and free from noise. How much Auto Focus has been improved is going to depend on what you are shooting and in what sort of lighting conditions you are working in. For me, the auto focus performance of the current 1DX is superb and it is really only difficult back-lit situations that pose an issue (from time-to-time). I wont know how the new EOS 1DX MKII performs in this regard until I get it out in the snow and ice in low light with a back lit subject.
The Canon EOS 1DX-MKII is now available for Pre-order with a delivery date of April 2016.