Well RX Vega graphics cards does look good on paper and can unsettle GTX 1080 and GTX 1070 but AMD still has no answer to the mighty GTX 1080 Ti.
Yes and AMD have one more problem, higher power consumption stop them to drop price of RX Vega and offer as affordable CF.
But you know AMD, they will offer some very attractive bundle with RX Vega, Crosshair VI Extreme and 1800X or even Zenith Extreme and 1950X and discount will be significant if someone use everything together.
Imagine ASUS Zenith, 1950X and ASUS RX Vega.
For me example power consumption is not problem, even for Tri Fire because of that I always advice people don't go below 850-1000W.
There is few models of 1KW in very small PC case and coud fit in smallest PC case with ATX PSU Support.
If we look total picture AMD still is not good in GPU section, they revive CPU line but GPU is still half dead.
Why is not good... Because they late 12 months to NVIDIA, and 12 months later, whole year, they can't offer same performance in similar power consumption as NVIDIA. Under normal circumstances we would expect AMD to beat TITAN Xp in 250-300W power consumption.
Now he will fight for market with GTX1080 and she need only 180W less... That mean you can power on almost SLI for RX Vega.
But I believe if they build so good Processors they could done and with Graphic processors.