Under the assumption that quantum computers can ever derive the private key from the public key.

On the other hand one could also argue that P2TR is more resistant to brute-force attacks than the hash-based addresses. The hashing algorithm used in P2PKH, P2WPKH... is RIPEMD160, which produces a 160 bit long hash. In principle, that means many different 256 bit private keys map to the same 160 bit hash (and therefore the same address). But a Taproot address consists of a 256 bit long compressed public key. That's much harder to brute-force.