I think not, fiat money will never be replaced by bitcoin.
because it is the tool we use for the current exchange, bitcoin is more suitable for the investment tool.
Yes Indeed, Fiat will never be replaced by bitcoin.Since in the New Era fiat or physical money is one of most useful tool in transaction, trading and so on. It will never replaced by an virtual money though it is one of a trend tools in the world still it will defest physical money since it is more convenient to use and proved and tested till this year. You are right about Bitcoin is more suitable for investment because it can be in a short and long term investment.
People that can never use digital money will always exist. Even when the cryptocurrencies come into our lives and become a part of them, fiat will be popular. Even the crypto fans prefer using it.