There is still a very bright future for digital currencies. The reasons being that, the world is moving and advancing so fast technologically that there is no way that people will continue to carry cash when there is a way that they can just pay online without having problems of what holding enough cash at that moment. It might take a whil ebut there will come a time where cash will die out and digital currencies will take over.
I think that cash will die out much earlier than everyone thinks. We will only have bank accounts and a crypto currency, and in the future we will refuse from banks, or crypto currency accounts will be managed by banks.