there is a GTX 1080 "GP-104-100" 60Mhs ETH
I'll believe that claim if I see it. There is no way they could DOUBLE the performance of a GTX 1080 on ETH while leaving it on GDDR 5x (excessive latency issues), and even if they moved it to GDDR 5 (not X) I doubt they could get it to 50 even with super-upgraded memory timings.
On the other hand, I've seen 30% power savings quoted for the GP104-100 - THAT seems possible, especially if they "factory undervolt" it at all compared to existing GTX 1080 cards.
That "60MHs" threw me off too and asked my contacts to provide some proof...
apparently NVIDIA has gone all out to get a killer mining card out with custom PCB, passive-cooling and custom ROMs.