I don't think cryptocurrency is ready to replace paper money. Before we even think about a world running on just digital money, governments all over the world will need to agree first on a global cryptocurrency that will be acceptable to all countries. Think of it as the digital version of the US Dollar or the Euro.

Do you think the US Government or the European Union will agree to let go of their own currencies in favor of a cryptocurrency that they cannot print on their own? How will they manage their country's interest rates if they cannot print paper money out of thin air?