Bitcoin can be used as an alternative to money but there are also many risks as Bitcoin is not limited to a specific price. As the price of Bitcoin is not stable, it cannot be compared to FIAT and the money savings cannot be relaxed like FIAT. Bitcoin is a powerful asset it can only be paid with Bitcoin as a perfect FIAT alternative for investing but Bitcoin cannot be used as a default currency to the exclusion of FIAT.
Bitcoin can just use for investment purpose so if we think that fiat will be replace if we use bitcoin for multiple uses then we are wrong because fiat has its own importance which cannot be fulfilled with the help of bitcoin.
Bitcoin is highly fluctuated currency whereas fiat does not posses any volatility. Fiat currency can used for daily uses whereas if we use bitcoin as a purchasing option then we will have to pay with different amount of bitcoin depends on the price of bitcoin. So I don't think that bitcoin can ever be consider better than fiat and also bitcoin cannot replace fiat at any stage of life.