In the recently announced Q1 2018 earnings report, AMD's CEO Lisa Su mentions that the company is already testing 7 nm Radeon Instinct GPUs, which should be sampling later this year. This GPU series is most likely part of the Vega 20 family that appeared in previously leaked roadmap slides. Spec-wise, the Instinct looks to be a solid competitor for Nvidia's Volta AI GPUs.
https://www.notebookcheck.net/The-7-nm-Vega-20-is-AMD-s-answer-to-Nvidia-s-Volta-AI-GPUs.301434.0.html