The empirical existence of rising marginal cost (as you point out) is not evidence of non-viability. Every economic 101 good is thought to be produced until its marginal cost is sloping upward. Economically coherent industries will continue to produce widgets. And increasing costs do not simply make an industry incoherent. Both social value ($demand/subsidization) and technology (cost/difficulty) come into play. It seems a bit arbitrary to make adverse assumptions about future ecosystems a bit more evidence.