Fiat will eventually collapse because it's just debt backed by debt. Hopefully when that happens, cryptos will take over.
No, fiat will never crash. It will exist as long as the state will exist. Own money is a sign of statehood. National money of the state interacts with the economy of this state, and the cryptocurrency is not capable of it by nature. Cryptocurrency can only go along with national money and cannot replace them, otherwise the economy of such a state will be completely unbalanced.