They will certainly become more mainstream over time than they are now.
But it's not that everyone suddenly will use crypto and fiat will completely disappear.
Can cryptocurrency/blockchain be a multi trillion dollar market long term? Yes i don't doubt that.
Will i eat my dick when btc doesn't go to 1M dollar per coin? No because it probably won't happen.
Yes. I believe that cryptos can in the distant future become generally acceptable like fiat currency. However, I believe that a great limitation remains the volatility of crypto prices. Therefore, I think the stable coins are more likely to go mainstream than the present tokens we have.
It will be, but it will be a matter of time till the mass audience accept it. I think, the major problem for crypto right now is the lack of actual interest from the mass. Furthermore, the price of crypto is easily manipulated, which had made it unstable to use as a mean of payment.
However, I believe in the outlook of crypto.