in the current economic climate, cost is everything. when things get better and customers disposable income goes back to what they use to be, im not sure people will still want the no frills. they may rather pay a bit extra and get a better service.
there will alwase be a market for no frills airlines as there are alwase going to be people who would not otherwise be able to afford to fly. however im not sure if it will be as big as it is currently once things get better. ryanair have realy made the most of the bad climate with its passangers. im not convicend they will be happy to stay loyal.