I would think so, though IV/sub-q held up quite well even with Tyvaso on the market and I believe it was Dr. Rubin who believe an Inhaled therapy would be the best way to treat the disease.
From an investment standpoint I think Oral in other indications may have the biggest potential. UTHR has tried/talked about Remodulin for other uses for some time and I'm not a science guy but a Prostacylin makes some sense in other cardiovascular indications.