An entry for the upcoming AMD Polaris 30-based Radeon RX 590 has been spotted on 3DMark by noted leakster TUM_APISAK. The new RX 590 is shown to sport higher clocks and is said to be using the same GDDR5 memory subsystem as the current Polaris 20 cards. Overall, the leaked benchmark shows conservative performance improvements over the RX 580.
https://www.notebookcheck.net/AMD-Radeon-RX-590-shows-up-on-3DMark-shows-less-than-10-improvement-in-scores-over-the-RX-580.337764.0.html
If is better than 1060 and cheaper than 1060 with 8gb.....
If you made the 580 on a 7nm node, as it currently is, it would be fall between 1070/1080 performance.
Given that Navi is a new arch, or one loosely based on GCN, and will use GDDR6, it will be in the 1080/1080ti range. (Closer to the 1080)
That's what next-gen consoles will offer.