since now 70D has great iso performance
Great ISO performance? From what I can tell, it's not significantly better than the 60D, which is similar to the 7D.
If you look at the JPG's straight from the camera, the 70D is significantly better than the 60D, but if you shoot RAW, the difference is very slight..... Far more computing power in the new camera (I think its around 17X) lets the 70D process the images a lot more in camera.
If you want image quality, I'd pick a 6D over a 70D any day of the week. If you want AF ability for quick moving objects, then the order would probably be 1DX, 5D3, 70D or 7D (order depending on if you shoot video), 60D, and finally 6D.... and if you want crop for more pixels on the target and want good AF and reasonable IQ, I'd wait for the 7D2...