Benchmark scores for 3D Mark's Time Spy have surface, and are purported to represent the performance level of an unidentified "Generic VGA" - which is being identified as AMD's new 12 nm Polaris revision. The RX 590 product name makes almost as much sense as it doesn't, though; for one, there's no real reason to release another entire RX 600 series, unless AMD is giving the 12 nm treatment to the entire lineup (which likely wouldn't happen, due to the investment in fabrication process redesign and node capacity required for such). As such, the RX 590 moniker makes sense if AMD is only looking to increase its competitiveness in the sub-$300 space as a stop-gap until they finally have a new graphics architecture up their shader sleeves.
Of course, the scores themselves are... Somewhat strange. The RX 590 in these scores, apparently running with a 1545 MHz clock (205 MHz higher than the RX 580's base boost clock) achieved a graphics score of 4,759 points. This is within spitting distance of known RX 580 scores (attributable to variance in benchmarking results, really), which could mostly reach these scores themselves - while overclocked over their boost clocks. The original poster, TUM_APISAK, has come out to say that the comparison scores in the pics are of two RX 590 graphics cards which are simply being misread by the benchmark suite.
The reported RX 590's call for fame is that its 1545 MHz clocks can be achieved at much lower power consumption figures than an overclocked RX 580 - and would likely be overcklockable on top of the base 1545 MHz, thus increasing the gap over the base clock % increase. Remember overlcocking gains aren't linear, though, and since it seems the RX 590 will still make use of GDDR5 memory (2000 MHz clocks; and again, remember the investment in repurposing the design for GDDR6), so you better push out your own manual memory overcklocking to improve on Polaris' most pressing limitation.