RELAX PEOPLE !
Market demand in a declining industry allows for smaller scale niche specialization startups. There are many examples of this; vacuum tubes, typewriter repair and vinyl records have all recently flurished again due to hipsters and their demand for analog products. Once a product lifecyle goes into decline, the market allows for smaller scalable companies to take advantage and sell lower-run products .
While current economies of scale don't allow small time businesses to price compete with giants like Abena or Harttman, if poly backed diapers go away, you better believe people will be starting diaper busineses to serve this community (maybe even me ? ) .
Of course they're going to cost more, but if the demand is there , people will pay (plus for many of the non-incontinent , this is just fetish gear for fun not function).
Short story long = not going away.