You can read yourself officially form AMD.
"In gaming, we successfully returned to the high-end market with the launch of our Radeon™ VII GPU in February 2019 and we are on track to introduce our next-generation “Navi” GPUs for the mainstream market later this year. "
BTW you own quote says the same "Whenever we’ve spoken to AMD’s AIB partners, and colleagues in the industry, the general consensus has been that Navi is going to be a 7nm mainstream GPU that will take the place of Polaris in the Radeon tech tree. "
Navi = Mainstrain
Vega 7nm =High-end (already launched)
The article assumption is based in this part...
"I asked David Wang specifically about Navi going toe-to-toe with Nvidia at the high-end of the market, and Dr. Su seems to be talking about the Turing-based cards from Nvidia when she says they’re going to be ‘right there in the mix.’ "
Well based in that quote he estimate Navi could be a little more powerful than expected... but right there in the mix is a bit ambiguous because nVidia RTX cards are there from RTX 2060 to RTX 2080TI... I'm a trully believer Navi will be better than RTX 2060 (and one version will trade direct blows)... but to be better than RTX 2080? No way... they are still threating Vega 7nm as their high-end solution.