The FE launch has been a disaster. It will still be so, even if they manage to pull off a miracle with RX Vega. They've already lost a non-negligible number of sales. Regardless of the official disclaimers, most people will believe (and not unreasonably so) that Vega FE will be within ~10% of RX Vega. These people are giving up on AMD and buying 1080 Ti's. They won't go back and buy a RX Vega even if the release day drivers boost gaming performance by enough to beat GP102.
No they haven't. Its going to be sold out for a long while after release.