If we subtract Satoshi’s 1 million BTC (as Plan B does in his STF2X model), should we also subtract the ~4 million BTC estimated to have been lost?
So that would make total supply around 16 million BTC. Some of these have a private key that is encrypted and the password forgotten, whereas others have lost the private key entirely, like the hard drive lost at the rubbish tip in Manchester in 2013 with a key for 800BTC on it. So the former will eventually be able to be brute-forced in coming decades when quantum computers can be accessed. But the lost keys are lost forever.
i'd be careful not to overestimate the number of lost bitcoin. Seems like people like to just assume any coins that haven't been moved since like 2012 or 2013 are lost, when that is clearly not the case. Proven by the fact that someone has for the past couple years been occasionally moving large amounts of bitcoin that haven't moved since 2010/2011. I forget the details but it has happened several times the past couple years. I generally assume maybe at 1.5-2 million, plus Satoshi's presumed 1 million, have been lost. This number of lost bitcoin will always increase by small amounts though because people will always unexpectedly die without having made arrangements for bitcoin they had in cold storage and no one will ever get access to them. Bitcoin is deflationary forever.