The most sensible rumors and AMD statements lead me to believe it will be 480/480x and substantially below 1070. Even below 1060 Ti. 970/390 performance level. Priced appropriately of course.
490/490x will be the lowest tier Vega coming out next year, and will compete against 1070/1080.
I don't think the Vega cards will be named like that, I think they will call them Fury again (Fury X2 / Fury 2 maybe).
The Polaris 10 is afaik the 490, because it has some shaders of its 2560 shader engine disabled (about 2300 usable). The 490X will have all shaders enabled, 2560. And i expect very high clocks, 1700 minimum and a maximum of 2000, maybe even more. With those speeds, it's easy to surpass Fury X and even 980 Ti performance. Hawaii with its 2816 cores and 1050-1100 MHz is just 20% slower than Fury X (maximum), now imagine a Hawaii with clocks of over 1700 MHz - yeah, now you know what I mean.
Also I think the 480(X) are the Polaris 11 GPUs. But maybe I'm wrong. But naming isn't overly important I'd say.
On the other hand, Pascal is a compute based engine, unlike Maxwell, so thats why Pascal is only a tad faster than 980 Ti, just by its big advantage 16nm resulting in clearly higher clocks. Give GM200 these clocks and it wins easily against 1080. GTX 1080 is no wonder GPU, all it's advantage is the better manufacturing process. Now imagine Maxwell with 6144 (double Titan X) or 5632 shaders (double 980 Ti), this would be nice (16nm 600mm² GPU). I think if Nvidia does a pure gaming architecture again, it will be like that - and a lot faster than Pascal. Just imagine, Maxwell on 16nm and with even higher performance per shader and more ROPs etc.