I doubt it could ever be proven to exist, though it might become better understood. Currently the dividing line between mind and body is the source of a lot of confusion, especially to the experts who delve into it in the most rigorous ways.
I think that free will only exists from a certain point of view, like qualia.
I’m an emergentist (though I don’t necessarily agree with everything in the Wikipedia article). I believe that physical facts at one level can give rise to higher-level phenomena. Nothing woo here, just physics at the root.
Simplest example is the gas law. While we can derive the large-scale behavior by tracking every molecule in the gas, it makes more sense to look at the higher level phenomena caused by that behavior. (Actually, it’s actually NOT possible to track every molecule … as we well know, thanks to uncertainty.)
Emergence doesn’t suspend or contradict any laws at a lower level. It just causes epiphenomena, where discussing it makes more sense at a higher level than reverting to the underlying level. It’s for this reason that while chemists need to know some fundamental quantum physics, they still speak in terms of chemistry rather than physics, most of the time. Likewise, cytobiologists don’t talk in terms of physics, but use the results of biochemistry to explore processes at the cellular level. If there ever is a solid science of psychology, it won’t be based on physics, but rather, it’ll be based on an understanding of neural processes as well as emotions, motivation, and other mental phenomena.
Free will is an epiphenomenon of sentience just as qualia like color are epiphenomena of sensation. The phsycialist explanation of color misses the subjective experience of qualia. It might predict that subjective experience exists (it doesn’t but maybe someday it might). Even then, it doesn’t completely explain it, as it can’t communicate what it’s like to experience it. (This is an oversimplification of The Knowledge Argument.)
IMHO, most discussions of TKA go off the track because people don’t seem to realize that qualia are epiphenomena created by the mechanics and act of sensation, and these epiphenomena only exist to the subjective entity doing the sensing.
Ditto for free will. From “outside”, it doesn’t exist. Run the program, over and over, and you get the same results (or there are random inputs, in which case it’s nondeterminstic, but still dictated by the physics and the odds).
But from the point of view of the consciousness created by the machinery, free will exists, just as the experience of the color red exists.
This may seem to be a pretty weak form of free will, since we appear to have no control. However, we are the entity created by the machinery and its inputs, and how we think creates those responses. This is the kind of “strange loop” discussed by Hofstadter in Goedel Escher & Bach.
We don’t escape from physics, but we are part of it.
On a tangent, we have to assume free will for ethical purposes, and for managing our own lives. That doesn’t mean it has to exist, though.