If Bitcoin replaced all the currency in the world, it would be worth less than $1 million per BTC. If the economy (and the value of a bitcoin) grows at 3% per year, then it will take more than 600 years for 1 BTC to go from $1 million to $100 trillion.
Anyway, I don't think that anyone disagrees that more decimal places may be needed at some point, but from what I've heard adding decimal places is easy.
Finally, there is no good reason for the money supply to be equal to GDP. It might be good to maintain the money supply at some fraction of GDP, but there is no way to determine what that fraction should be.
According to my calcultions about 750.000$ (current purchasing power of the $), which may grow to 1m$ but i highly doubt it as we face a severe recession / depression if these central banks print money like crazy.
If GDP will be lost, which will be as if the riots will break out then alot of property could be damaged, so let's just go with 750.000$ cap at best.
Now obviously not all money will go to bitcoin, you cant force 100% of the population to use it, my estimate is that at it's best it could be perhaps 40% of the world population, and thats still in optimal results, not to say about other cryptos that could replace bitcoin.
So if this is true then we will definitely need 5 more digits so that we could do commerce on the small scale too.
But my idea is to keep the names of the units "mBTC" "satoshi" "cBTC" and such, and just name the other 5 digits like 1 "Gavin" or 1 "Maxwell" or whatever from the main developers. So that it should not be confusing to new members, if we would rename 1 satoshi to the 0.000000000001 decimal it would be pretty confusing.
Well there are many arguments for keeping the supply = gdp, which i wont discuss here, but it just more efficient that way. Of course in bitcoin we can't do that so we can only play with the decimals.
