The coming recession will drive everyone to use ULCCs and the legacies will go bankrupt, just like last time. Lol NOT.
This time the legacies have better pricing power and they will be able to make their money in places ULCCs can't touch. They'll be able to outcompete the ULCCs in contested markets, which is what they were expected to do last time, before everyone realized that overcapacity combined with 2000 era Orbitz style websites totally disarmed them.
ULCCs will be forced into mergers and I expect one Frankenstein of a company will be powerful enough to hold on to some vital markets, but the segment as a whole will shrink.