What next? Several more airlines will fail or merge. Most or all of the rest will also start charging to check bags. Fares will rise. Leisure fares will rise the most. Service will be cut--most severely to leisure destinations. Airline workers will lose their jobs. What amenities are left will disappear or will be charged for. Everything they can do to reduce the weight of the aircraft will be done, including such seemingly insignificant things as carrying less water to flush the toilets. Seat-pocket magazines will disappear unless their weight can be justified by the price paid for the advertising in them. New, lighter, less comfortable seats will be installed with the lowest possible distance between rows. Aircraft will only be fueled for multiple segments under unusual circumstances in order to keep the gross weight lower. This will mean more frequent fueling, taking more time. Cruising speeds will be slowed in order to save fuel, thereby lengthening flights. Some smaller cities will lose service altogether. Wages in the industry will not keep up with those in the economy as a whole, thereby undermining morale and negatively affecting service.
And that's just the beginning of "what's next." Some of these things are actually happening already.