to me the future of paper money is still ok and there is nothing wrong to it, as majority of the people of the world still using paper money and it will take still a lot of time that people start using bitcoin for shopping, therefore we can say that still there is nothing wrong to paper money.
Because it is simple to use paper money, people will prefer to use it than bitcoin or any digital currency for their daily lives. Bitcoin is only good for online transactions and we know that not all people are not into online, and maybe majority of the people does not transact online.