I think it is a mistake to license anything under a “or later version” license. If you do that, you licence your code under a license that you have never read, so how can you know that it serves your intentions? You are blindly licensing code under a licence that has yet to be written! In the GPL case, the Free Software Foundation states that “The Free Software Foundation may publish revised and/or new versions of th…
What is the worst case scenario, by the way? You could say it depends on who you are. One such scenario would be for developers who agree with the FSF's strong copyleft philosophy who are betrayed by a future hypothetical revision that removes all copyleft provisions to make it no stronger than, e.g., BSD. This affects only a subset of those choosing a license for their project. (I.e., if you don't care about copyleft, this purportedly horrific thing doesn't even affect you.) Funnily enough, the subset of those who would be affected are hardly ever the ones I see making the argument you are.
So what terrible things do you imagine the worst case scenario involving?