Theoretically, at least. http://www.bit-tech.net/news/hardware/2016/07/05/radeon-rx-480-4gb-8gb-flash/1
While some will obviously be happy with their free surprise I can't help but think that AMD have been all over the place with this launch. I'll definitely be waiting until at least 6 months after the 1060 arrives to see where everything stands and what the prices have done in that time. Once I build I won't be looking to upgrade for several years so I don't need to rush now.
AtiWinFlash with Polaris support now out, for anyone wishing to test if 4GB becomes 8GB, TPU vBios DB has 8GB ROM for ref PCB which all AIBs currently use . https://www.techpowerup.com/downloads/2728/atiflash-2-74 *** edit *** TPU article OCuk/AMD Reddit also have a thread, so some successful 4GB > 8GB conversions , shame about the awful power distribution on pcb .