[dsp1234]

GNU projects belong to GNU/FSF

The only documentation that I see[0] about this just says "The program remains a GNU package unless/until the GNU project decides to decommission it.", but that's not a legal document. Assigning the copyright to the FSF would be a good indicator, but is not actually required to be a GNU package. So unless they have some other document to sign, then this seems to be a mutual contract which can be terminated by either party at any time. I don't know if that document exists (if it does, you'd think they'd link it on that page so people could review it), but if it doesn't, then I don't see any reason why the original submitter can't revoke GNU package status, like any other business relationship.

[0] - https://www.gnu.org/help/evaluation.en.html