Actually… what would even be the result of the pure MLKEM document getting dropped by the IETF? I guess the entries would temporarily be marked deprecated or something, until another reference is made available somewhere, describing the same behavior? I'm not sure what procedural blockers this might run into but my general sense is that the IETF & IANA wouldn't "block off" the already allocated codepoints from being specified elsewhere (or allocate new duplicate codepoints) so long as the behavior is identical.
Good question.
If the document is dropped by the IETF, nothing at all would happen. It's already a valid code point registration, and indeed the authors could have just published the document, registered the code points, and stopped (see: https://datatracker.ietf.org/doc/draft-barnes-tls-this-could...).
If the authors decided to later pick up the document somewhere else, then they could probably get the reference changed to whatever that was, as long as the semantics were identical.