it could happen because along with the times and technology that will grow very rapidly but of course it needs a process and a long and difficult time of course
I think that fiat will not be able to completely disappear even in the distant future. Many people love to diversify their funds and they will still hold some of the money in the form of paper money.
I agree with you that Fiat will continue to exist but it is side by side with cryptocurrency and I think it will be better than replaced fiat.
I will also do things that I will definitely save some fiat.