Bitcoin is not here to replace fiat, bitcoin is here to help our in our lives.
My hope is that bitcoin will someday be the main currency for transactions.
That would be the best.
Bitcoin can never replace fiat, bitcoin will be used as currency but it will never replace fiat, as there are few things that only fiat can take care of, bitcoin will be popular but will not used as a major currency, people have more faith in fiat and they are used to it, so they will never support bitcoins.