Didn't Indigo buy a major stake in WoW? The same company that finances Frontier, WizzAir and JetSmart, the real undercutters in all markets with 430 Airbus A320NEO family on order. If you complain about Norwegian, you haven't heard from WizzAir apparently. And WoW is joining that family.
On the other hand, Norwegian might fail or not fail, but there are airlines queuing up to buy it, for over a year already, so it probably won't leave the market. Outfits like IAG, that owns AOCs in the UK, Spain, Austria, France and Ireland.