Jim,
I can' t answer your questions as to the logistics of the manufacturing process and it may actually differ from one manufacturer to another. But if I understand the underlying question of future availability of a given film format, then at present I can relate that there are several suppliers of specialty film formats. The cost is often prohibative, however. For instance, I was seriously considering building a 10X16 format camera and the cost in lots of 5 boxes minimum was 180.00 per box of 25 sheets. I can purchase 12X20 film at a slightly lower cost. Hope this addresses your question and thoughts.