Cash will never go away. I am sure that is true. Reason:
1 / Not every country is modern enough not to use cash.
2 / The world is still very poor and they only use cash.
3 / Cryptocurrency is facing the challenge of being hacked and used to serve money laundering purposes.
And it will take a long time before everyone in the world is able to have some kind of computer .
Or even if they have a computer but they don't have the money to replace it when it breaks down , that would mean they couldn't spend money till they buy a new one.
But i do believe a significant portion of the payments will move to crypto.