An Asia region based guy called Lau Kin Lam figured it's ok to break NDA. He posted photos of an XFX Radeon RX 580 which he liquid cooled, and sure posted benchmarks as well.
Accompanied by photos, screenshots and a video you'll notice the Radeon RX 580 clocked at 1360 MHz, all info and screenshots can be found on his facebook page. Lau seems to be an enthusiast overclocker who has attended several competitions, with ties to HKEPC. His OC Result for RX580:
Time Spy 4622
Graphics score 4664
Graphics Test 1 31.53FPS
Graphics Test 2 25.93FPS
He also posted a Youtube Video called NDA BREAK - RX580 where he livestream an hour session taking the card though benchmarks and overclocking. In the pictures below you can see some more findings with scores overclocked as well.
HIS Radeon RX 570 IceQ X2 Already Selling - 04/12/2017 06:30 PM
A Vietnamese retailer seems to be already unreleased Radeon RX 500 graphics cards, and it seems that the folks from from a Vietnamese website called Genk went ahead and purchased a HIS Radeon RX 570 ...
AMD Radeon RX 500 Series Launches April 18th - 04/12/2017 12:34 PM
We've been chatting about the upcoming Radeon RX 550, 570 and 580 graphics cards for a while now. the one thing that never solidified however is the actuality release date. That myth is now debunked ...