Previous rumors were saying that Navi would only match the GTX 1080 GPUs from Nvidia, and, according to some new information, this is more like a half truth. It looks like AMD is planning to release the mid-range Navi 12 in the first half of 2019, with the Navi 10 and 20 high-end models coming in late 2019.
https://www.notebookcheck.net/New-details-on-the-upcoming-AMD-Navi-gaming-GPUs-emerge.360511.0.html