1+ stop better ISO than what?
Better than the current 18mp sensor - which Canon has been reusing for four years now.
And the 1DX quality sensor will never be in a 70D or 7D Mark II.
Canon will certainly not put the 1DX sensor in a lower camera.
You have to realize, though, that Canon has been using a 10+ years old manufacturing process for their senors.
This has been confirmed by Chipworks
, who put various Canon sensors under a microscope (literally).
Sooner rather than later, Canon will switch to a more modern manufacturing process.
When that happens, we'll see noticeable improvements in image quality compared to previous sensors.
So, the question is, when will Canon make the switch?
Is it going to be with the 70D, 7DII, or some of the higher end cameras.