Although apparently slower than both the NVIDIA GeForce RTX 3090 and RTX 3080 by 19% and 4%, the upcoming AMD Radeon RX 6900 XT (apparently a reference design board was used in the tests) is around 13% faster than the RX 6800 XT and no less than 35% faster than the RX 6800. However, it seems like the retail version will be faster.
https://www.notebookcheck.net/AMD-Radeon-RX-6900-XT-OpenCL-benchmarks-13-faster-than-the-RX-6800-XT-and-35-faster-than-the-RX-6800.507658.0.html