Seems pretty clear with MS messaging of "premium" in regards to Scorpio that it will be $499.
People thinking a PS5 will roll out in 2018 with even more power upgrades are just silly. The PS5 would be $599 or even $699 with the specs that people seem to hope/guess at in 2018. At that point, the Scorpio would be able to drop from $499 to $449 or even $399.
Like others have said the Scorpio will probably be at $499. If MS wanted to just blow up the whole marketplace and really just go after Sony, they would release it at $349-$399. But, $349-$399 would be a monster money loser...
It is near the end of the end....