The basic principle of copyright is that it is in the public interest to allow creators of content to control the usage of their works for a set period of time -- in theory, this spurs creative production, which is good for society, so society has an interest in fostering it. However, there's a balancing act involved: copyright typically spurs creation but hinders usage of content, since almost by definition it is imposing restrictions on how you can use it. The fulcrum of this balance is how long the copyright term is. Currently, US law is approaching entirely ridiculous levels (many decades of protection); the Pirate Party is trying to push *way* back. (Probably further than is likely to happen, but it's not a bad place to start negotiating from.)
The argument from the FSF seems to be that copyleft is fundamentally different (and better) than ordinary copyright, and should therefore be exempt from such restrictions, but I'm not sure I buy it. The underlying philosophical principles apply -- you encourage people to create works by giving them control over those works for a time. In this case, the control just happens to be in the other direction: preventing people from hiding their use, rather than preventing them from using it. But it's still all about allowing the content creator to restrict how people use their works, to provide motivation to create.
Of course, there's the argument that the GPL is somehow more moral than other forms of copyright, but I just plain don't agree: I find that argument more religious than practical. To me, the *really* moral high ground is something like the more generous MIT license, which I summarize as, "Here's some code; do what you like with it; don't sue us." (If it isn't clear from the above, I just plain don't like the GPL much -- I think it's crappy legal language and way too hung up with its crusading message.) From a pure social-utilitarian POV (which to me is usually the firmest ground for writing law), it makes more sense to free the code completely after five years, so more projects can make use of it.
So I don't see any strong reason to make an exception for the GPL in the proposed changes. Opinions? I actually have no idea which licenses my geek friends prefer, and I'm rather curious.
(Disclaimer for all of the above: IANAL, just an interested and moderately informed layman...)