Maybe, but I'm still disappointed that since the rumors of a Rivers set started swirling last year and there was the possibility for it coming out at the end of 2010, instead we've seen reissues of Ellington and the MJQ. Not to denigrate those sets, but it just seems to me that the Rivers stuff, because it has been much less available, is far more significant musically and historically. As a huge Mosaic fan I want to see them continue to produce more sets in the mold of Braxton, Threadgill, and Carter/Bradford, among others. To me there's a lot more potential for growth there than there is in going over the more mainstream stuff from the 1950s and 1960s.
That said, I'll probably get the MJQ at some point because it is not music that I own (except for maybe one or two albums). But it doesn't generate the same kind of excitement for me as a Rivers set would have.
I see your point and I'm looking forward to the Sam Set too, but I wouldn't denigrate the musical or historical significance of having coherent reissues of the Duke or the MJQ. Especially the Duke set, which is the first coherent reissue of this material on CD, and the first of any kind for 30 years or more. And as many people have pointed out, the bigger names probably subsidize the Rivers , Threadgills and Carter/Bradfords to some extent.