Unless AMD went back to the drawing board and completely ditched their existing technology, then shrouded the entire thing in secrecy (like they did with Ryzen) then it is always possible to predict next gen performance by simply doing the correct maths.
One thing known about Vega was the die size etc and range of cores it would have. Take this (and other bits and bobs like HBM2) and it is possible to roughly pen out how it *should* perform.
Then you take the logic that nearly everything touted about a CPU/GPU is BS pre launch *but* some of it is always spot on and you have the truth hidden in there somewhere.
I've not just been saying this for a few days. I have been saying this to you guys on this forum for months and months. Vega will be similar to a 1070.
Now from what I am hearing there are going to be three SKUs for Vega. However, even that is not known to be true yet so it could just be one, like the Fury X, which was then used to make three cards (Fury, Nano & Fury X). All three were hardly any better than each other, Nano just sucked for throttling so needed water.
So my prediction is still the same. Vega will perform somewhere between a 1070 and maybe as high as a 1080. Unless AMD are hiding anything up their sleeve then that will be Vega.
But this recent notion that Vega will be as fast as a 1080Ti is just nonsense. That, I can promise you, *IS* all BS created by the Hype Train (tm).