There are a number of small tweaks to existing algorithms that could be used to keep ahead of quantum computers. For example increasing the key length by 4x would require a larger number of qubits therefore slowing down the risk.
And the popular symmetric key crypto and hashing algs are known to be safe. So even without exotic new post-quantum crypto we can have a good amount of battle tested existing tools.
This is all valid points, except we can't predict how fast the number of qubits in a quantum computer will grow. Moore's law, even for classical computers, is just unscientific, in my opinion.
Also, quantum mechanics is not only about making computers faster, protocols safer, simulations and measurements more precise.
Quantum physics can shift how we view our reality. It can make possible what was unthinkable and unimaginable. Quantum teleportation, counterfactual computation and communication, quantum pseudo-telepathy and much more is just magic for a "classical" observer.
And the popular symmetric key crypto and hashing algs are known to be safe. So even without exotic new post-quantum crypto we can have a good amount of battle tested existing tools.
https://en.m.wikipedia.org/wiki/Post-quantum_cryptography