If the 7D MKII will have a crop sensor, I do not understand how the camera will have as good of high ISO performance as the full frame 5D MKIII.
The 5DIII is made on Canon's current CMOS manufacturing process - which is quite ancient and is well overdue for replacement.
The hope is that the 7DII sensor will be manufactured on a new manufacturing process.
If that's the case, the 7DII sensor will likely perform the same (or even better) than the 5DIII sensor. Of course Canon will eventually make FF sensors on the new manufacturing process and FF will again pull ahead in performance.
If that is the case, what do you think happen to current 5D III? You think Canon going to let that happen?
A new technology has to be introduced somewhere. Since sales of lower end cameras far exceed that of higher end cameras, it would make sense that a new technology gets introduced into the lower end cameras first.... like the 6D which has GPS, touchscreen, and a lower light central focus point than the 5D3...
It is almost certain that this new technology will outperform the old process.... by how much remains to be seen... perhaps even approaching the sensitivity of the 5D3. It is also almost certain that this new camera will outperform the 5D3 live-view focus....
What does this mean for the 5D3? Nothing! People who want FF are not going to trade in a 5D3 for a crop camera, just like those who wish a crop camera are not going to go FF.... there is a market for both. What it does mean is that a 5D4 will probably use this new technology and you can expect the 5D4 to be better than the 5D3 like a 7D2 outperforms a 7D.
Keep in mind 7D was designed for speed, not so much high ISO. I can see 7D II might have 61pts AF like 5D III and an increase in frame rate(maybe 10-fps). BUT NOT IN HIGH ISO or LOW LIGHT like 5D III, regardless what the new sensor might be.
Canon will not put 7D II in near 5D III in term of high ISO/LOW LIGHT. 5D III is only 1yr old plus, it still have another 3-4yrs more before we seeing any rumors 5D 4.
Keep in mind, the original debate was high ISO - not DR or others features etc....