Ask HN: What if a technological advance makes all existing cryptocoins obsolete?

You can't just say "What if" and then describe something plausible that has mostly predictable consequences, as if the question's profound just for being asked. This will probably happen! What specifically do you want to know about the consequences?

No-one's satisfied with the protocol of any cryptocurrency right now. Transaction rates are very low, proof of work algorithms are ridiculous, the decentralized protocols are still incurring emergent centralization.

So there'll be new protocols, and the price of coins running on the old protocols will presumably decrease eventually.

However, something like Bitcoin could be adapted on the fly to gain newer protocols, which has already been happening somewhat. You just have to persuade the majority of miners to adopt the change. In that case, the coin could retain value rather than become obsolete.