It would be a utopia economy, if you understand what I mean. Such a scenario can never exist because that would mean everyone would learn how to use the internet. This is highly impossible. There are old dudes or even young people who aren't Internet compliant. Also, there are some underdeveloped countries where electricity is a huge problem. Bitcoin can only remain a currency for a selected few. After all, its supply isn't even much. Just a mere 21million is really too small for the entire world if it were to be used as the only global currency.