A solution that Jimbo suggested for a similar problem
on wikinews, was
to require not only all contributions to be licensed under the
gfdl/cc/whatever but also a proviso that by editing you agree to allow
wikimedia to put your contributions under any license they want.
So it
will always be gfdl/cc for ever no matter what wikimedia does or says,
but it can also be relicensed under a different license so that (for
example) it could be easily distributed in the .dict fromat.
It's a nice idea... but contract law would not allow it. Somehow, you
can't accept to accept anything...
But there are solutions for a massive licence change. For example, I
suggest to begin by offering dual licensing for new articles and
editing. With a bit of time, more and more contributors would agree
to change the license of their content. With good tagging, you could
certainly keep a trace of licence changes and wait for the moment
there will be enough dual licenses to begin removing the old licensed
content.
Also it would be very important for wikipedia to provide its own
license and to allow it to evolve. As a policy matter, I don't
believe it's really safe to leave your legal needs within the hands
of others like we did with the GNU/FDL (and it would be the same
problem with CC).
Jean-Baptiste Soufron
CNRS-CERSA Paris 2
http://soufron.free.fr