I am not a cryptographer myself so maybe here we are just discussing on a normal guy's level. As far I know, quantum computing really has the potential to successfully decrypt the private keys and therefore can be the biggest threat to Bitcoin. In the past few days, this topic got spread around because Google announced that they already have the technology at hand which many of us supposed should still be years ahead. Now, there is that fear in the Bitcoin community on quantum computing and whether this can really be utilized against Bitcoin which can be its end. Nobody can really be sure if the quantum computing developed by Google can effectively be the one to stop Bitcoin. This can be the one we can only wait and watch. As the technology is on the hands of Google, I don't think they will be irresponsible to just use it indiscriminately as this will have many legal repercussions which the company will not want to go through. On the other hand, we have to remember that if there is a demand someone will eventually fill the shoes therefore we should be expecting developers to come up with ways to counteract the power of quantum computing to balance things out. And this can actually make things exciting.
If you are a cryptographer you must have known about this way before most "common folk" that recently panicked over this "news". I do not believe what they say that Satoshi did not know about this, i'm sure that was discussed back then, i certainly knew and i am no cryptographer or cypherpunk tho i did read their writings from time to time.
This was very theoretical as you say, and people were already writing programs that would run in these theoretical machines, years later there were even simulations with classic computers (which of course were way too slow but they were just testing concepts anyway).
Well this was years ago, and time didn't stop. If google didn't mention a thing (like IBM), did you think no advances were being made? I clearly remember when the first few qbit machines started becoming operational, but of course almost nobody knew what that meant...
But here, years later, you bring the exact same excuse. Its still theoretical, lets wait. Actually, the wait is over, the writing is on the wall. Panic is for fools, there is still time to act, but act you must, not sit still and wait the next decade to learn that, sure, some agencies already are decoding everything online.
There are proposed mitigations to improve Bitcoin resistance to quantum attack, those should be revisited, now that there is time, and not wait for later.
We are still too far from quantum crypto (hardware unavailable to the masses), but even that should be considered. This is the solution to quantum breaking crypto, this side most people don't know a thing about either. But in the meantime, those (classic computer) algos that make it hard for quantum attacks, should be implemented. Transition times indeed...