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