Never say never. Let's not forget one thing - there is nothing infinite in the world. The state and social foundations that exist now can be completely reformatted and changed within one decade.
We do not know what the world will be like in 10 years, everything will depend on technology.
If we move into a fully digital era, then there will be no point in fiat means, they will also try to go into a fully digital environment, but during this transition there may be problems that simply destroy the fiat in the form in which we know it.
I really hope this is not going to happen. For me it's all about the control of the government. Crypto currencies were designed to be independent from governments. A digital FIAT currency will still be at the mercy of it's central bank. It's up to the politician of how much new money is being issued every month. With cryptos it's a fixed process and every investors knows before hand. I would appreciate if not a few people can decide the faith of so many.