I think there's potential for cryptocurrencies to find homes in the modern financial landscape. But your counterpoint (a) is based on network effects. Distinguishing between short-term bubble behavior and long-term resilience can only be done after knocking the system with crises. Is there hope? Sure. Is it demonstrated? Absolutely not.

There is one feature gold has over Bitcoin that cryptocurrencies cannot replicate: resilience across technological domains. Gold holds value without computers or electricity. Bitcoin does not. Gold, on the other hand, cannot travel at the speed of light. TL; DR each solves different systems of trade-offs.