I probably need a bit more context for the question.
The existential threat from quantum is probably a future one. It's not a current one, in the sense that it's actually a threat to the cryptographic systems in place that we currently use to operate all of our systems.
I'm trying to avoid getting too technical here.
A future possibility is that quantum computing could effectively undermine all modern encryption techniques and shorten the lifespan, if you will, of how long something could be considered cryptographically safe. That threat isn't current. It might be 10 or 20 years away, to be blunt. Certainly people who champion quantum technology would argue that it could be just around the corner. They're not wrong. The reality is that it's probably quite some distance in the future.
The threat, though, is still real today in the sense that if it's cracked in 20 or 25 years, we would probably have quantum-safe cryptography available by that point. However, the existing stuff that's currently being secured by modern encryption becomes vulnerable 20 years from now. If it's stored some place in an encrypted way and we think it's safe for the next 2,000 years, it could become vulnerable at that point. All of that legacy encrypted data that we consider very secure at this point could become very vulnerable at that point. Much of it could be released or hacked into and be sitting out some place. It could become vulnerable at that stage.
I'm not sure if I've actually answered the core of your question. It's a very complicated one.