The people who will first have access to sufficient quantum computing power (to hack bitcoin) will be the entities that created it, e.g. university research departments, government labs, major technology corporations, etc. These people will likely not use the technology for nefarious purposes, and they will have access to the technology long before the bad actors will.
How does this help the scenario thought by OP? It would be enough for such an University or Laboratory to publicly declare a win against Bitcoin and then to see all the weak Addresses emptied out. This alone would cause enough chaos for the progress of Bitcoin to be set back years in my opinion. Only because they are not Criminals themselves it does not mean they can not cause abrupt chaos for Bitcoin if and when they have the 'key' to what is thought Satoshi initially held.