1. Nvidia won't be releasing any new desktop GPU's anytime soon. Nvidia is skipping 12nm, that is more than obvious now, since if they weren't skipping it they would have been shipping their their xx70 and xx80 series already, GDDR6 has been available since February 2018, by now most memory manufacturers have it in plenty of supply, 12nm technology has been ready for over 6 months now, sampling up to one year before.
2. Even if Nvidia released new 12nm GPU's in the summer, there is NO WAY that a GTX 2070 would be faster than a GTX 1080ti. Okay? From 28nm to 16nm tsmc finfet process is over 50% more efficient, 16nm to 12nm you are looking at a basically refined 16nm process, with about 10 to 15% more efficient. Lets put it at best case scenario where they can extract 15% more performance at the same power envelope, where is the other 40% going to come from? GTX 1080ti is over 50% faster than a GTX 1070. How would a GTX 2070 reach GTX 1080ti levels if the node shrink gives at best 15% performance boost at same power?
3. It doesn't make financial.business sense to release new GPU's right now. Cryptocurrency is still going quite well, its not what it used to be, you won't get rich quick off of it, but its still profitable, within a year miners can return the cost of their mining rigs and turn a decent profit, and that is in the first year alone. So there is still demand for GPU's. If its not crypto that drives sales, then its gaming and Nvidia is selling out all of their GPU's. With the 16nm process so mature, yields are amazing, so they are racking in record profits.
As I've predicted since October of 2017 and have been posting it ever since, Nvidia is most likely going to go straight to 7nm process, this gives them enough time to gather a ton of GDDR6, GDDR5x, etc... supply, gives them plenty of time to sell current graphics at record profits, the 7nm process is about 50% more efficient than 16nm process, so it will give a similar performance boost as 16nm did over 28nm, it allows them to better create and tune their next desktop architecture and would allow them to sell similarly sized, priced and powered GPU's.
So GTX 2060/70/80/etc... would be the same die size, same power envelope as current gen, but about 30-40% faster.
GTX 2060 > GTX 1070 at 120w at $250
GTX 2070 > GTX 1080 at 150w at $380
GTX 2080 > GTX 1080ti at 200w at $550
GTX 2080ti > Volta at 250W at $750
I expect each model with the lower number to be slightly faster than the current higher model number. So the GTX 2060 would likely be about 5-10% faster than a GTX 1070.