I think another possibility that will happen is, Banknotes are still valid, digital currency may be considered valid by every Bank in the world, but may require a very long and long process, it could be successful if approved by the Government and bank banks in each country, Security risk! This may be a constraint, because it will be the generation of new breeders of account breakers or IDs, as has happened to some ATM machines, but with Bitcoin as a digital currency may add some Privacy like password hint and other sebainya, while public money will interact as usual
that is the short term possibility , in the future paper money might completely get disappeared.
as everything could be done digitally , people will think about why they still need an outdated one? as technology basically help our lives into better and easier . paper money also are not environmentally friendly , technology could completely takeover our daily lives.