Since I'm a "Stallman-was-Right" kind of guy, part of me would certainly like to.
But I'm not sure what problem of today or the immediate future that this would be solving.
I think that the language core as Apache2 is fine. Ren Garden was/is GPL, and new projects like online web tutorials/tools/games might want to be as well...to avoid clones that don't give back. But I don't think there's a terribly large risk of divergent development on Ren-C source. If anything, there's the opposite problem, of Oldes working on the old R3-Alpha source...but there, at least with compatible licenses we don't have to bother with worrying about copying or attributing fixes or code back and forth.
Also, not that it is likely to ever wind up in a court, but if it did...it would just introduce a lot of murk. In any case it's likely to matter, it would matter in a bad way. If someone decides to be antagonistic or adversarial and say "oh, I take back my contribution" or something. Better to just have everyone on the same page and no murk...it was released Apache2, and stayed that way, and nothing dicey happened in the history.
So I'd say stick with Apache2 for language core and libRebol. But certainly any new large efforts in a meaningful app or extension should consider going with a more restrictive license. But the direction of licensing changes needs to always be from more restrictive to more permissive, not the other way around.