Your GFDL contributions will fall into the public domain 70 years after your death anyway. Why wait? Why not release them right now? I found the idea quite liberating, actually.
The FDL idea is, of course, more anti-copyright than the public domain idea, because it is intended to convince others to release their content openly. It turns copyright against itself - the only freedom it takes away is the freedom to exert control over content. The FDL has various problems (GNU is primarily about software, and hasn't really spent much work on developing decent general open content licenses), and other licenses aren't established enough.
The copyleft concept only works well with a standardized license. Neither GNU nor Creative Commons will give that to us. I do believe that Wikipedia's use of the FDL will give it a big boost, and that we can increasingly use that as an argument that the FDL *is* the standard share- alike license. Isn't that amazing - we're already so big that we can argue that something we do is right because we do it. Almost like Microsoft ;-)
Regards,
Erik