FR have to reduce capacity and that is very hard.
I bet they could continue the expansion at the present speed, but only under certain conditions. They have to get more passengers willing to pay more for the flights. Why not continue selling 70-80% of seats very cheaply, many people do need them, as affirmed above. But in order to serve the passengers in the vicinity of numerous minor airports in FR network, it's pointless to offer them just cheap point-to-point flights. These passengers are ready to pay almost the same amount of money they pay to LH, SAS, Air France just to be able to travel using more suitable and more diverse connections therefrom. But, of course, not limited just to a couple of selected destinations they are being offered. That's the Ryanair's chance (still unacknowledged by MOL). These pax are not so price-sensitive, they can fill some of the "free seats" paying reasonable money. For their sake it could become even acceptable to introduce FR connecting flights to Amadeus or alike (yes, paying the comissions) - in order to get them aboard.
As I said before, it would require re-modelling of the entire FR concept. But with the wise planning, it's possible. I've envisaged HHN as such a central airport where flights from every destination meet. Such a hub function would also improve the financial situation of the airport, the transferring passengers would provide money, the airport would not be forced to introduce any additional charges as it's probably going to happen now. Regrettably, HHN appears to be the next place for FR to burn the bridges. Quo vadis, Ryanair?
P.S. I know the opinions of many. It's not the FR model. MOL prefers just the simple cost-effective solutions, the frills like connecting flights do not fit at all. Maybe, but the limits of this system are now becoming more apparent than ever. The enterprise always has to be flexible and at times some very radical approaches are simply unavoidable.