According to rumors, AMD's Navi-based GPUs, which are slotted for release in 2019, may compete with Nvidia's GTX 1080 but not supercede it. This could spell trouble for AMD; the GPU shortage caused by the cryptomining craze particularly hit AMD's stock, and the lack of a competitive GPU next year may cause a loss of market share.
https://www.notebookcheck.net/AMD-s-upcoming-7nm-Navi-GPUs-may-not-be-more-powerful-than-Nvidia-s-GTX-1080.299072.0.html