Paper money will stay forever.
Why? Because its easier to make than coins.
Paper money is still there because bitcoin is made due to the needs in the digital world. Many of us is thinking what comes tomorrow because they are afraid that everything will be replaced by technology. However I'm still believe that paper money will last forever.
in fact bitcoin is still not too much introduce throughout the world to be use for everything. therefore I think the importance of fiat currency is still there and I think it will continue for a long time because I am sure that it will take decades when all the people of the world will start using bitcoin for shopping and for everyting just like fiat currency.