There's no good reason to believe that quantum computers will break modern cryptography.
Shor's algorithm requires that a quantum Fourier transform is applied to the integer to be factored. The QFT essentially takes quantum data with a representation that mirrors ordinary binary, and maps it to a representation that encodes information in quantum phase (an angle).
The precision in phase needed to perform an accurate QFT scales EXPONENTIALLY with the number of qubits you're trying to transform. You manage to develop a quantum computer capable of factoring my keys? Fine, I'll add 11 bits to my key length, come back when you've developed a computer with 2000x the phase precision.
Regulators require a transition to quantum-safe algorithms. In the EU, systems labeled as "highly important" must complete the transition by 2030; so you have to do it regardless of how quantum computers evolve.
But I still think it’s a good idea to start switching over to post-quantum encryption, because the lead time is so high. It could easily take a full 10 years to fully implement the transition and we don’t want to be scrambling to start after Q-day.
Moving from SHA-1 to SHA-2 took ~20 years - and that's the "happy path", because SHA-2 is a drop-in replacement.
The post-quantum transition is more complex: keys and signatures are larger; KEM is a cryptographic primitive with a different interface; stateful signature algorithms require special treatment for state handling. It can easily take more than 20 years.