well, i think btc with a 16 trillion marketcap is possible to happen but at least by 2033 or so but at the end it's all about the trust, i agree that a currency can't b just 21 million pieces but why not b the satoshi it's much much more than 21 million pieces?, i believe that satoshi nakamoto wanted btc to serve as a currency & the way i can see it happen is through the usage of satoshi instead of full btcs but again it's all about trust & the 2 materials i can think of that people kept trusting n them for thousands of years r gold & silver, so f hundreds of years from now btc is still trusted by people it will join gold & silver, on the other hand btc usage as a reserve is already happening n some places & believe it will continue & spread n more major countries -US, china, russia, germany, japan, etc. again it's all about trust & no one knows the future but we try to predict. nice post- well done, have a great day