Jet fuel is expensive. It doesn't matter if there's 7 billion people or 11 billion, if they can't afford a plane ticket none of this matters. We have to spend incredible amounts of money building new airplanes, developing new technologies, costs which get passed on to consumers in one way or another, and just assuming there'll be some explosion of aviation is extremely short-sighted IMO. It's more like a very delicate balance between many factors that are constantly trying to pull the industry in opposite directions (efficient airframes with more px vs. paid-for airframes, and many others).