Dear mrasr,
Cryptos are great but I hope and think that it will not exist as the only way to pay/sell various things. I like cash better and probably there will always be more options and not only one. So fiat (therefor cash) and crypto will be used. It is always better to have different options and you can choose than having only one possibility imo.
Great post anyway.
Yours truly,
Gandalf The White