this is fascinating. i'd chuck jungian theories about collective unconscious into the mix as well. (but then, you know i'd say that ).
I'm not convinced that free will isn't a red herring dilemma, like nature vs nurture (some of both, morons!), or demanding the existence of god be proven (don't hammer a nail with a screwdriver). So I don't think it actually has a place on a list of mysteries that will be answered in the near future. But evidently there are people who think otherwise.
My guess is free will vs determinism will turn out to be a "some of both" answer.
I do think that what Jung calls a collective unconscious will be found to have a proven scientific basis, though. It's like the firmware of the human brain.