Even though Vega is out and Navi is around bend, AMD may not be finished tapping its Polaris GPU architecture for a new round of graphics cards. Just poke your head in the rumor mill and you'll hear rumblings of Polaris 30. We have only vague references to go on, but Polaris 30 is said to be shipping sometime soon.
Let's back up a moment and look at the existing Polaris architectures. For anyone who hasn't been following the codenames, the Radeon RX 480 and Radeon RX 470 are Polaris 10 parts, Polaris 10 is built on a 14-nanometer FinFET Low Power Plus processor, otherwise designated as 14LPP. Polaris 10 features 2,304 stream processors and 36 compute units (CUs), and supports up to 8GB of GDDR5 memory.
AMD then refreshed its Polaris architecture last year with new Radeon RX 580 and Radeon RX 570 graphics cards, with Polaris 20 GPUs underneath the hood. Built on a 14LPP+ manufacturing process, Polaris 20 is essentially an updated revision of Polaris 10, which AMD optimized to achieve higher clockspeeds. Both Polaris 20 and 10 are comprised of around 5.7 billion transistors, with a die size of 232 mm2.
This brings us to Polaris 30. Based on past naming conventions, Polaris 30 will be used in upcoming Radeon RX 680 and Radeon RX 670 graphics cards. Rumor has it Polaris 30 will be manufacturing on a 12nm node, and offer around a 15 percent performance boost. If true, we would also expect a bump in clockspeed, and likely better power efficiency as well.
Take all this with a grain of salt, however, as most of the information available originates from a source on a Chinese web forum. The same source says Polaris will be "released soon," so take from that what you will.