I am guessing here, but I suspect that Stanley Pranin had a much closer relationship with Morihiro Saito than with Kisshomaru or Moriteru Ueshiba. I also suspect that very few Japanese who practice aikido have copies of the bilingual commentary. So I think that the Stevens translation is all that the overseas aikido community will get any time soon.
I don't think I truly understood how rare Budo was. At least English speakers have a translation. I guess that means that as a Japanese speaker one would have to be content with Saito's partial commentary for AikiNews.
Sort of related to that, I wonder if the demand has reached the point where it would be attractive to publishers to go the extra mile and publish more in a bilingual format. Again AikiNews seems to be at the forefront with their reissue of Saito's work. I wonder if the larger market offsets the additional cost.