I think this is true to some extent. However, when you license under the GPL, you have the option to say, "Version 2", "Version 2 or later". If you're leary about how the license may change in the future, you are free to just say it is licensed under that specific version.
That opens up a different can of worms, though.
If you released under GPL2 only and GPL3 comes out and you like the changes it makes, you're theoretically going to have to go around to all your contributors and get their unanimous approval to change the license their code is released under. All it takes is one of them to say "nope, I only licensed my contributions under GPL2 and refuse to permit GPL3" - or they can just not reply - to derail your proposed license change.
