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:
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.
Basically with 3DMark Time Spy he reaches:
Radeon RX 580 Benchmarks Leak In Asia