With details…

21 years from inception would lead to 2030

Back then a rough estimation of USD M2 for 2030 would have been close to 21T USD (so called Covid QE brought us there much faster, but the M2 has retracted since)

To cover these 21T (more or less taking into consideration coins still left to mine after 2030, not much) Bitcoin would need to be worth 1M, or 1 cent per sat.

Sat cent parity and same market cap, the flip can happen.

Maybe world gdp is a better target…