Years ago I read about the potential danger of quantum computing for Bitcoin,
for thousands of years (yes, even before computers) we have been coming up with newer and stronger cryptographic schemes to make it stronger as efficient ways were found to break the older ones. this is not going to stop here either, it will be a constant battle of strengthening cryptography while technology improves.
so what does it mean for bitcoin? nothing really! like everything else bitcoin has to also upgrade its cryptography at some point to be ahead of the technology.
Indeed. What you just said implies a "potential" threat. But the existence of quantum computers hasn't even been realized yet. A potential threat is as good as not a threat since contingencies can be basically done to prevent it from being a "threat". Besides, even in the recent news of Google and their quantum computers, the current progress is much smaller than what quantum computers should really be able to. They just state it's possibilities in the future but it hasn't really been realized as of yet.