To do a full post-QC’ing, yes, but that doesn’t mean we cannot start.
While we cannot today decide whether a future Bitcoin community will fork to freeze non-QC-safe coins, it seems likely they will (a Bitcoin with a few million extra coins is almost certainly value-ruining).
Given this, we can start to move now - adding a hash-based signature opcode to tap script allows wallets to, today, transparently and for free, ensure their coins remain spendable in the face of such a future.
