Paper money still exist in the future even dihital currency would ve more popular because not all people can have this decentralized currency that is ehy paper money is much usable to them for daily needs.
It depends. If we can promote bitcoin and spread it worldwide then there isn't really much of a use for paper currency, especially when they are issued by a government and costing them so much to issue.
Governments could even move onto cryptocurrencies themselves, to save the printing fees.