Wrong. Vega will replace the Fury line, which competes with the Titan/Ti line. Which Nvidia will release just in time to compete with Vega.
These Polaris cards won't even beat the 1070, and at only $399, the 1070 is mainstream. It's the upper end of mainstream, but mainstream nonetheless. Also, we will see the 1060 in the next month or two to compete directly against these Polaris cards at $299
Maybe, maybe not. What proof do you have for your stipulations?
In my opinion, the Fury (non X) was a direct response from AMD to the 980. It was better than the 980, but also more expensive. However, the Fury X wasn't better than the 980ti, at least for the first six or so months. So depending on how you see it, whether you think a loss or a win constitutes direct competition, the Fury cards were 980 competitors and succeeded or they were 980ti/Titan X competitors and failed.
How I see it (AMD winning):
Fury Nano > 970 (small form factor, low power consumption, high performance)
Fury > 980 (high-end air cooled GPU)
980ti > Fury X (enthusiast GPU)
With that in mind, Vega 10 will compete with 1080 while Vega 11 will compete with Titanium edition 1080. The 1070 is a mystery to me at the moment as we don't know its specifications or performance. Is it going to be as close to the 1080 as the 970 was to the 980? Based on the reported TFLOPS performance, the 1070 will be more like a slightly overclocked 980ti while the 1080 will be more like overclocked 980 SLI.
You could also see it differently (nVidia winning):
980 > Fury Nano (the overclocking headroom of the 980 makes it a better GPU)
980ti > Fury (the Fury only beats the 980ti in certain DX12 tests)
Titan X > Fury X (the Fury X only beats the Titan X in certain DX12 tests)
I personally don't see it that way, though. The Fury X was never supposed to compete with the Titan X. I'm sure if AMD charged over $1000 for a GPU, they could also have made an absolute beast—they did so with the 295X2 and Pro Duo. However, they chose not to. Why? Because their competition was the 980 and 980ti.