I also have an RX 6800 XT and I plan to keep using it for many years to come. It's a great performer and won't have any VRAM limitations like my R9 Fury did. I think that it'll be at least a decade before 16GB isn't enough and that's assuming that there will ever be a time when 16GB isn't enough. I say that because it's already more than enough for Unreal Engine 5 which is essentially photo-realistic. You can't get much better than that.
Actually, the RX 6800 XT would be the bottleneck there, especially at 1440p, not the R9-5900X. See, the RX 6800 XT is the performance equal of the RTX 3080 and TechPowerUp has these results for the R9-5900X with an RTX 3080. I'll use 1080p because the game will be completely GPU bottlenecked at 1440p:
So you see here that your R9-5900X is tied with my R7-5800X3D with an RTX 4080, so our two rigs would be equal in performance because we both have RX 6800 XTs. However, if we had a more powerful card, like an RTX 3090 Ti for example:
All other things being equal, your CPU's output increased by 7.5% which means that the RTX 3080 was the bottleneck here. While it's true that Cyberpunk is pretty hard on GPUs, it's only 1080p here and if the RTX 3080 is the bottleneck at 1080p in Cyberpunk, then it would definitely be the bottleneck in
almost all modern titles at 1440p. Exceptions to this would be real-time strategy games like Civilization because it relies completely on the CPU for game speed. I often joke that the ideal setup for Civilization 6 would be a Threadripper coupled with an RX 580.
If the performance increases at the same resolution with a faster GPU, it means that the CPU isn't the bottleneck so your R9-5900X is just fine. Even with the bottleneck, you're still looking at ~60FPS at 1440p with the RX 6800 XT in Cyberpunk 2077, certainly nothing worth upgrading any time soon. That game is often considered to be a "worst-case-scenario" for Radeon cards so other games would be even better. Here's a Cyberpunk demo at 1440p using an R9-5950X (which is pretty much the same as the R9-5900X in gaming) and an RX 6800 XT: