In some cases and in some countries yes.That bitcoin cannot replace fiat because they still needed it.Countries that are banning bitcoin in their country is a reason why fiat is still needed.Proper introduction and use of bitcoin for them can be a factor in order that bitcoin be used.
i think it is wrong, bitcoin can replace the fiat money in the future but yes it will take a time to replace but it does not means that bitcoin can not. the fait money is now get a value in the market of the world and the bitcoin is a new rising currency while passing the many stages at very good result. there is wiat to become bitcoin legal than it will replace the fiat money easily.