Likely Crypto currencies will remain in the background but find a solid dark web home. The birth and success of the Amazon phenomenon has almost guaranteed the dollar as the future and besides, it is the backing of Crypto in the first place.
I agree with Tecoyah. Currencies like Bitcoin will remain a thing for black market and big ticket white market items in online shopping as well as a goto for criminal transactions but for every day stuff, nation state backed currencies will remain dominant.
I believe the current cryptocurrencies will fade away but I think eventually cryptocurrency will replace currencies like the US dollar. How many transactions, each week do you do using no physical currency? Do you still carry cash?
One day countries will stop printing currency and minting coins.