2031 sounds a bit late for me. Generally speaking, it is possible that a some point bitcoin basically plateaus (at much higher levels) and would be going up and down just 20-30% a year.
What I am talking about? I cannot imagine bitcoin going at a 45 degree angle for a decade, but it is possible that bitcoin will very rapidly change it's "state" from a 0.5 tril asset to a 10-20 tril asset (20-40X) and stay there for a long time. This transition could be relatively fast-for example, this cycle and the next one, finished by late 2028, early 2029.
I am not sure why we need to compare bitcoin with GDP when it is mostly an asset that is presumed to be a savings vehicle, at least for now.
We have roughly 500-900 tril in assets and, I believe, bitcoin could be roughly 2-3% of all assets.
In addition, Gold has a 13.1 tril market cap and by 2028 halving, bitcoin's stock to flow (indicating scarcity) would be way higher than gold, making it quite plausible that bitcoin can attain a similar market cap.
Both gold and bitcoin are not directly involved in GDP production, or are involved only on a limited basis, for now.