but what about the wallets that is using these weak RNG or even bad entropy back in the day? So Should people we worry more about that than quantum threats?
Threat of using wallet with bad RNG or entropy source always been exist, where it usually can be brute-forced or cracked without quantum computer.
And just curious do you think that the post Quantum crypto wallet will ever become a mainstream ?
The changes need to be done on protocol level, where Bitcoin protocol need to be upgraded to support quantum-resistant cryptography and add address format if needed. Afterwards, we'll see Bitcoin wallet supporting it.