The 7Dm2 appears to be a significant upgrade over the 7D in AF system and frame rate ( not looking at the video side since that is not meaningful to me, but may be meaningful to others). Until there are some in the field, and Roger Cicala gets to evaluate the precision of the new AF system, we won't know how much of an improvement the AF system is over the 7D.
As for the sensor, given the pixel count is identical to the 70D, and both have DP tech in them, the odds are it is at least a derivative of the 70D's sensor. What we don't know is how much Canon can do with this sensor; there can easily be features that could have been in the 70D that were deliberately disabled so they could be used in this camera. We won't know anything about the relative sensor performance until there are a significant number of 7Dm2 bodies in the field. Personally, I was hoping for a 15 or 16Mp sensor with at least 1/2 f-stop high ISO performance boost in RAW.
Based on published specs, the 7Dm2 is a solid upgrade over the 7D, and sits at a good price point. I have owned my 7D for nearly 5 years, it is a very good all-around camera. The 7D is also at its best when coupled with the best glass; this should not be discounted and I have found this out the hard way. I will be very interested in seeing what kind of sensor performance skilled users can drag out of the 20.2Mp sensor; I have gotten much more skilled over the years in maximizing the 18Mp sensor for indoor sports, outdoor sports, and birding. I have also gotten much more skilled in maximizing the performance of the 19pt AF system ( staying away from situations known to frustrate it ).