Eureka Video hasn't updated their web page for this, so I doubt anyone will know the speaker until that happens, or the disc gets reviewed. I haven't seen any reviews for it, have you? For the non-commentary disc, yeah, but not the one you're speaking of.
Strange that they're both listed as having the same release date. Hmmm.
As awful as it sounds, my money is on Jeffrey Lyons, since he did the Americand disc. One more irony for Welles' career: the biggest whore of a critic being asked to do a commentary for one of the greatest filmmakers.
I'll email BlackStar, maybe they can get somebody to take a look.