The current expectation is it will be a combination of sigstore and TUF, but if someone proposes something better then we're open to that.
Implementing those things takes time though.
Implementing those things takes time though.
Pypi should just be the organized repository of packages, with only some limited assurance over their authenticity. That is, pypi should just let authors upload signatures and metadata.
Something else, something to plug into pip (taking into account also the bootstrap problem), should be responsible for validating the signatures and providing assurance over identities.
People that just want TOFU will use that one plugin. People that trust Microsoft will use the github plugin. People that trust pypi also for identity, will use maybe what you will write when you have time for it. Maybe a popular plugin will allow people to choose many IdPs. Over time, the community will converge and that may be adopted as de facto standard.
But your choice of removing PGP signatures (as on type of signature) is now making that impossible, and you intend to decide in the future for others what the only blessed verification mechanism is (also, with no indication of when that will happen).
PyPI should implement it though, because fundamentally the question of who is authorized to release for "requests" on PyPI is a question of who PyPI authorizes to release for that.