I can't guarantee that it won't fully happen in the future, but as of right now, given the pace at which cryptocurrencies are being adopted globally, I doubt that this will be attainable in a few decades. Why? Because there will still be a government. Such an event won't take place due to the government's need for total control. However, if the majority of the top countries use and leverage the profit for economic development, this is still achievable. With additional nations adopting it, the entire world will eventually do so, I'm confident. Also currently, there hasn't yet been any formidable step to show that it will soon replace debit and credit cards.