There still be some value, but much less. There are two types of crypto uses, legitimate and speculators. Legitimate users do use it for what's intended, commercial transactions. Speculators just want to buy low sell high. Most users are speculators, and the'd abandon crypto if that were to happen. Among legitimate users the main use for crypto is international transfers, that's what I personally use it for. Buy in one country, immediately sell in another. Far faster and cheaper than banks. But this also relies on being able to convert to fiat, and the existence of a large market, which needs speculators. That would only leave a small sector of legitimate users that transact in crypto. The value of crypto is the sum of these two. Intrinsic value (from legitimate users) plus speculative.