Expected to arrive in the third quarter of this year, it seems that not all the members of the upcoming family of AMD Navi-based video cards will show up at once. The Radeon Instinct, based on the Navi 20 GPU, has been apparently delayed to early 2020. However, the mainstream Navi GPUs might be available just in time for this year's winter holiday season.
https://www.notebookcheck.net/Navi-20-based-AMD-Radeon-Instinct-delayed-to-Q1-2020.420173.0.html