There will still be some people who use fiat currencies.
Would you like me to mail you a letter with more thoughts on this?
Or you could read my editorial in the newspaper the next time you sit down and flip through the pages.
If Bitcoin ever did become mainstream do you really think fiat would still be used?
Just like my 75 year old mother likes to send letters once or twice a year...some people will enjoy using their dollars (though it will probably be hundreds of dollars) to buy things. They will eventually go the way of those that still paid for things in gold pieces until fiat replaced them.