If you're going to judge by the images, then it's likely you won't see a difference (that can be attributed to the camera) between shots taken with the 70D and shots taken with the 7D2. At anything but the highest ISOs, you probably won't really be able to see a difference between the 7D2 and the 7D, either.
Once you get to this level, the differences in the camera start to matter for how easy it is to get the shot, rather than how good the shot is. And since the 7D and 70D are already very, very good, the advantages of the 7D2 are likely to be limited, in the general case, to the most demanding of environments.
This means that if you really want to see what the differences are between the cameras, you're going to have to use them yourself, preferably in the most demanding environments you operate in.
I wouldn't be just looking at the IQ of the image, but the actual shot taken. If people start putting up fabulous action shots for instance, then I will be quite excited by the camera's auto focus and tracking etc. I'm hoping noise will be better, but aren't we all. I also use this site to see what can be done by better photographers than myself and to inspire myself to do better. I already have owned a 7D for several years so I know reasonably well what it can do.
So for me the nearest I can get to seeing what the camera is capable of isn't with a technical review, but in seeing what can be created by users on this forum.
I have seen the early images produced by the 7DII and read comments saying "they look great", then read "no they're not! you haven't taken X,Y and Z into account", this is followed up by, "ah, you obviously don't understand exactly what X,Y, and Z represent" ..........and so it goes on. I like to look at pictures, so I guess I will have to wait a little longer unless someone wants to lend me their 7DII for a few days