The RX 6800 GPU particularly efficient when it comes to undervolting, as its TGP can be reduced by 45 W down to 183 W. These figures are already laptop-friendly if we look at Nvidia's RTX 2080 Super mobility GPUs, so we can expect to see an RX 6800M GPU with 150-180W TGPs that matches the performance of a desktop-grade RTX 2080 Ti soon.
https://www.notebookcheck.net/Undervolted-AMD-RX-6800-with-183-W-TGP-offers-clues-about-an-upcoming-RX-6800M-laptop-grade-GPU-matching-the-desktop-RTX-2080-Ti.505084.0.html