The codenames for the upcoming Vega 20 and Vega 12 GPUs were mentioned in the latest LLVM and Clang compiler patches. Codenamed GFX906, the Vega 20 will support native AI instructions and the patch information reveals that it will benefit from the 7 nm tech, while the Vega 12 codenamed GFX904 is rumored to be replacing the Polaris series (Radeon RX 580 and co.) later this year.
https://www.notebookcheck.net/Mysterious-AMD-Vega-12-GPU-info-leaks-out-plus-Vega-20-AI-features.302274.0.html