If there will be a quantum computer powerful enough to crack the private keys, bitcoin will be least of your problems. Because that will be end of privacy as we know it, and we need to quickly solve how to protect every freaking system against quantum attacks.
That would only be in the movies creating a quantum computer model alone will consume a lot of money just to crack what belongs to someone else because I don't see the essence of why someone will want to crack satoshi wallet, and the moment that is archived their is no way that it won't affect bitcoin in anyway because people will feel their asset is no longer safe, and privacy is very important when it comes to bitcoin, and even if their is a way the government will definitely disallow it.
We are decade away from a powerful quantum computer to give private key cracking a shot, and even with that it could take decades to crack 256 bit encryption.
And their more years for them to actually archive thay and even if it was archived do you think it will be in the possession of anyone the government and other organizations will have access to such a computer because the harm thay it does is more than the good that it will be used for because the characteristics of that computer is beyond human imagination. So their a lot of considerations to be made.