Boris Rose is the jazz preservation hero who recorded tons of material (radio broadcasts mainly) from the late '40s into the '80s. He is the one who recorded Bird (and many others) at the Royal Roost, Lester Young, Count Basie and many others at Birdland. Also Charles Mingus, Cecil Taylor, etc...
Some of his tapes were released on bootleg albums (a few made it on very legal releases).
There is a lot of the material which still remains dormant. Mosaic would have a hard time in getting authorisations from participants if they were ever to try releasing sets from these tapes.
One can still dream