I think Canon (and any other sensor manufacturer) will need to make a major technical breakthrough to seriously increase high ISO image quality in cropped sensor cameras from where they have been the last couple of years. From what I can tell, Canon hasn't done much to surpass the high ISO quality of the 7D, which is a 3 year old camera at this point. I wouldn't hold my breath waiting for the 7DmkII to be seriously better at high ISO than the current lineup of cropped sensor cameras, whether it's the 70D, 60D or 7D you are comparing it to (except perhaps for improved in-camera JPG NR processing, which is not a true improvement to my way of thinking).
The 6D (or 5DmkIII) are significant improvements in this respect, there really is no comparison. It will be interesting to see if there are improvements to be had in the next generation of the 5D series, which we may not see for a couple years yet. So, realistically, if you want improved high ISO performance today or in the foreseeable future, the 6D is the logical choice, hands down (or the 5DmkIII if you want more features).