i have no idea what the bold part means.
but i don't think decentralized cryptocurrencies such as bitcoin can kill the centralized fiat. fiat as we know it may change form and become a cryptocurrency but the "cash" or paper money will always exist and be used the same way that fiat turned into digital form with debit cards, credit cards and internet banking but cash still exists.
I think so.Cryptocurrency will grow continuesly and supporting each other with cash or paper money.
Under decentralized system and blockchain technology used , they will be more famous in the future , widely used all over the world by many related business or institutions.Crypto may be more known in non cash or electronic transactions while cash transactions will be used mostly at small scale transactions like traditional markets and small business.