Misunderstanding the objection; blaming the wrong party?

"Not only does it violate the assumption that the author of the work decides what license to use, it adds another party to the equation."

You always had the option to not contribute to projects licensed in a way you don't agree with, including projects that choose "or any later version" which means some other (arbitrarily different) terms could apply. No "specific choice" has disappeared because one could have chosen to license their work under a specific version of the GFDL that doesn't allow for other later versions to be used instead. It's safe to assume licensees will read the license before they choose to license works to others. Courts will certainly assume that if it comes down to it.

Perhaps I'm not seeing the real objection here, but it seems to me the entire objection here is wrong-headed and aimed at the wrong party. Once one agrees to licensing terms they haven't read (such as licensing which allows licensees to pick "any later version" or somesuch wording) anything can happen; you're choosing to trust the unknown. If you believe your trust was misplaced you have nobody but yourself to blame for this.

In the case of GFDL 1.3 we're being given far more detail about the license migration than with the GPL (which the poster said "seemed like a worthy place to put my trust"). GFDL 1.3 tells us what the specific other license is (CC's By-SA 3.0) and we know that after August 1, 2009 the relicensing deal is off. When you consider that CC-By-SA 3.0 is more vague than this, this poster's complaint seems aimed at the wrong party.

This poster's complaint would be far better directed at Creative Commons. Read section 4b of the By-SA 3.0 license and see how many different licenses one can choose to relicense publicly-performed adaptations under. The number of licenses is ill-defined because one of the conditions is unknown as I type this (section 4.b.iv): the definition of "Creative Commons Compatible License" is vague and CC has not yet defined any licenses as compatible with By-SA 3.0. They could do so at any time and then any CC-By-SA 3.0 licensed publicly-performed adaptation could be migrated again to that license. You might not like what they have chosen as "compatible", what they consider to posess "the same License Elements", or some mistake they made in a "jurisdiction" license alleged-equivalent. The FSF doesn't endorse translations of its licenses for this very reason.