Until it’s not. Nobody has proven any of these schemes to be secure against quantum attack. Post-quantum (today) just means that nobody has proven that the problem is equivalent to a problem that quantum computing can solve efficiently. This article is about LWE being proven breakable. Others will follow. The security of these schemes rests mostly upon the lack of researchers that understand them and quantum computing well enough to approach an equivalence class proof. Example: elliptic curve isogenies.