Lol, the quantum computing is a myth. Even if the quantum computing become a reality the bitcoin community will always implement a new algorithm to be quantum proof. Quantum computing is more of a fantasy than a reality. I think it would take more than 100 years for it to actually work.
That may have been the prognosis a couple decades ago, but today cryptographers mostly agree quantum computing will start threatening various signature algorithms sometime in the 2020s.
I'm sure Bitcoin will scrap ECDSA for a better algorithm when it becomes necessary, but it's something we need to plan for
soon. The bigger Bitcoin gets, the more damaging and difficult to coordinate an emergency hard fork could be (especially where a rollback is required).