To perhaps state the obvious, the main threat of Store-Now-Decrypt-Later is that long-term secrets may be exposed.

For secrets like "where is the secret underground military base?", this is obviously bad - you'd need to build a whole new secret underground military base somewhere else.

For secrets like "what is the private key of my bitcoin wallet?", it's actually a whole lot less bad. If you know that the secret is at-risk in advance, you can move the funds to somewhere quantum-secure, before it becomes an actual problem.

So the question becomes, "will we know which secrets are at-risk in advance"?

For the threat of quantum computing, I say Yes. We already know it's a possibility, and cryptographers are working on building and migrating to quantum-resistant systems. There isn't going to be a sudden overnight crypto-apocalypse, they're just going to get gradually better. Weak crypto (like RSA-512) that we already know not to use will fall first, acting as an early warning signal.

It's very possible (if not likely) that nation-states etc. will be secretive about their quantum computing capabilities, and might take us by surprise one day. But the same is also true for classical cryptanalysis, and it hasn't yet (to my knowledge?) caused us any financial crises.

This is a very interesting question, but the resolution will be difficult. In what domain would this happen? Commercial bankig, SWIFT, cryptocurrencies?