I would actually be quite interested in hearing the new K612's and see what is different coming from the K601's.
Personally, and I currently own both, I much prefer the K601's to the K701's purely sonically speaking. I find the 701's to be much too harsh to my ears for any kind of extended listening. The highs give the perception of more detail on the 701's, but I feel it to be more of a falsified sensation than necessarily one of a truer nature (this compared to the 601's). The only positive I have been able to gain from the 701's is their pad design. . .I got a 2nd pair of 701 pads and use them on the 601's, which tweaked the 601's just enough acoustically to be that middle pot of porridge. (Goldilocks reference in case you missing it, ha) I have always felt like the 601's were the overlooked redheaded step brother to the 701's personally.
I have only stated all of this (and wasted the last few moments of your life while reading this) to give insight into the reasoning behind my interest in the new K612's. I would be interested in, both, to see if there was a gain in sound quality over the K601's and also to see if it gets, possibly sadly, over stepped for the K712's in a similar fashion to its ancestor.
as a side note. . .I actually only still have the 701's from a lack of motivation to sell them, ha