yeah I suspect a Vega clocked higher will edge out a 1080 (not the 1080 with the GDDR5X)
I see Nvidia refreshing the 1070 with the faster memory in response and cutting production on any 1070/1080 that does not have GDDR5X which should already be happening for the 1080.
All GTX 1080's has GDDR5X memory.