You can start a "grass-roots" dual licensing campaign; there is no need for a project-wide policy change. Simply convince Wikipedians to release their contributions under a second license and to put a statement to that effect on their user page.
In that case, I would argue for straight public domain as the second "license". It's the only way to cut through the maze of slightly incompatible free/open/creative commons licenses that is bound to become almost as stifling as standard proprietary copyrights. Throw fair-use materials in the mix and it becomes an utter mess to sort out who can use what.
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.
Axel
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