While I certainly wouldn't countenance this on a per-project basis, wouldn't it make sense to unilaterally assign all of one's copyrights to a third party (for example, the Free Software Foundation or Software in the Public Interest) in a will to ensure that the copyright remains in the hands of those who will ensure it remains Free, and to also permit relicensing of it under a new Free licence should that be required (e.g. GPLv6).
In the absence of explicitly assigning copyright, what would happen in normal circumstances? Does it become public domain, or the property of someone else (e.g. family, dependents, government)? It's something I would definitely consider when it comes to making a will, and I hope I'm not alone in wanting to know more about what the best options are for ensuring one's works are kept Free.