Earlier quoted context omitted.
If you assume powerful quantum computers then Bitcoin is dead, that is a straightforward result. The digital signatures that prevent others from spending your bitcoins are based on elliptic curve cryptography (ECC). The security of elliptic curve cryptography is based on the hardness of the discrete logarithm problem (DLP). A sufficiently powerful quantum computer can use a variant of Shor’s algorithm to solve the DL…
Single-use P2PKH addresses are quantum safe, since the public key is not revealed publicly until spending, just its hash. QC breaks ECDSA but not SHA256.
I believe you could scaffold up a system even with a 1-send limit that transparently functions the same as what currently exists since you can issue transactions to multiple parties within a single send, but that largely kills Bitcoin as normally used. All but the most sophisticated users would be required to hand over control of their wallet to actually manage the massive proliferation of addresses needed to act as if you have more than a 1-send limit. But sure, you are technically correct that there exists a very narrow use case which you can probably hijack aggressively enough to salvage the system if you tried hard enough.