So, it has been raining rumors about this for a while now, and I am 99.99% certain that it is a true thing. AMD is going to release a refresh for Polaris. The third iteration will be based on 12nm (previously 14nm). The first card released would be the Rx 570 refresh announced by next week already, followed by the RX 580 at 12nm a few weeks later.

PCOnline now as well mentions this, and they claim to have the info from videocard manufacturers. Polaris 30 (I'll just call it that for now) is manufactured at 12 nm and could be 10 to 15 percent faster compared to the current RX 570 and 580. The current generation is built on 14 nm FinFET LPP+. When AMD moves to a 12nm part, the clocks could indeed be bumped up a bit more, much like what Zen+ is doing for Ryzen 2000. It's not the first time that this rumor now has surfaced and for now, we do believe them to be true. 

12nm AMD Polaris Up and Coming Alright - Pretty Soon Already