I do wonder what would have happened in the counterfactual world in which the FSF put out a new version of the GPL annually, with minor changes in each version, rather than a big revision one time. A slow ratchet, together with the guarantee of forward-compatibility.

I also wonder whether many people would have refused to use the GPL if it had had the "or any later version" built in and unremovable, rather than making it part of the license grant.