Caporegime
Well that rumoured FP16 performance puts it at about two 480's which is not as quick as the 1080, let alone the TitanX or even Volta.
Your Talking about Crosfire scaling, making a GPU twice the size is not Crossfire.
The GTX 1080 is 85% faster than the RX 480, a chip 2x the size of an RX 470 + 20% should beat the 1080, this based on the Polaris architecture, which of course its not.
https://www.techpowerup.com/reviews/AMD/RX_480/24.html