(due to address reusage or P2PK etc.)
Aren't we using public key in P2TR outputs as well?
For me, the ideal migration path is: first nudging users even more to not reuse addresses, like with such warnings like proposed in this thread, to reduce the number of vulnerable coins, and then implement post-quantum cryptography optionally once it is mature enough and we have a clear candidate.
I'm not against this approach (even though I don't think it works, people will ignore the warning) but I say the security of Bitcoin as a whole doesn't rely on how many addresses are vulnerable. It is based on whether any of them are. In other words if one address were vulnerable then the whole system would have been considered vulnerable.
So even if we manage to encourage majority of the users to avoid address reuse (like 90% of address reusers) there are still going to be 10% reusing addresses and if their coins were to be stolen people won't say "those who reused address lost coins", they will instead say "bitcoin is vulnerable" and the catastrophe (specially price-wise) will happen nonetheless.
This is why I've always said the move to a new algorithm should be done through a hard fork with a deadline and any coins that don't move before that deadline should be considered unspendable.