Digital currency/bitcoin will never replace money and people will still use the paper money because The paper currency will never be replaced.
Paper money is ruling the world since its inception and no other currency can replace it in future, people are more comfortable in using fiat rather going for digital stuff.
but it looks like the changing times will change someone's more comfortable paying for something instantly via cell phone or laptop. not offline and deal face to face with the seller. the human need for more and more if you have a solid course you will need to purchase and pay distress offline. bitcoin will be very useful