Whether cryptocurrency will completely replace cash is a complex question and depends on several factors:

1. **Adoption Rates:** Cryptocurrency adoption is growing, but it is still far from being universally accepted as a replacement for cash. The speed and extent of adoption will play a crucial role in determining if and when cryptocurrency could replace cash.

2. **Regulatory Environment:** Governments and regulatory bodies around the world are still developing frameworks to govern cryptocurrencies. Regulation will heavily influence the integration of cryptocurrencies into mainstream financial systems and their potential to replace cash.

3. **Technological Advancements:** Improvements in blockchain technology, scalability, security, and user-friendliness of cryptocurrencies will be critical for broader adoption.

4. **User Preferences:** Public trust and confidence in cryptocurrencies need to increase. Many people still prefer the tangibility and familiarity of cash over digital currencies.

5. **Economic Stability:** The stability of cryptocurrencies as a store of value and medium of exchange is another significant factor. Volatility has been a challenge for cryptocurrencies, making them less attractive as a substitute for stable cash.

Given these factors, while it's possible that cryptocurrencies may become more widely used in the future, a complete replacement of cash in the near term seems unlikely. Cash serves essential functions in economies worldwide, and any transition to a cashless society, if it happens, would likely be gradual and contingent on the resolution of current challenges facing cryptocurrencies.