Thanks for the recent adds to this discussion. I've taken away something from each comment.
Even with these useful insights there is still the matter of the majority of these recordings are still in vinyl. One can say, "Well, the same problem occurred with 78s - lots of music just drifted off into history." Here's the difference - recording had advanced in the 50s, 60s and 70s leaving us with very good sound.
SO ... my question remains - is this very good sounding jazz disappearing? Will streaming services pick up the vinyl and include it in their offering? Or, using the resources suggested by @rok2id will I also be chasing down vinyl (I've got a basement filled with it already!!!).
Great conversation.