Obviously the shortage is real... if you define shortage as more worldwide demand for airline pilots than there is availability of qualified pilots.
It should also be obvious that the shortage has not hit the US legacies and majors... yet. It will have to get pretty bad for, say, Delta or FedEx or Southwest to run out of qualified applicants. I would think, that before you got to that point, there would be a pretty catastrophic rearranging to the entire airline industry. More than 50% of the flying in the US is done by "regional" airlines. If the regionals start feeling the pinch badly enough than the legacies may start having to start covering some of that flying with mainline... or at least start paying their regional pilots salaries commensurate with the majors. In the end there is a certain demand for available seat miles, and a certain number of pilots available and in pipeline. When the two don't match up the only solutions are a) cut back capacity, b) increase the number of pilots in the pipeline, or c) operate larger aircraft so the passenger to pilot ratio increases.
a) is not likely... too much money to be made from each passenger
b) is the the long term solution, but airlines are notoriously short-sighted and the ramp-up needed to be 4 years ago.
c) is where this industry is headed right at the moment in the US... small RJ's replaced with large RJ's, large RJ's replaced with mainline. A319's replaced with A321's etc. Fuel cost is driving the industry in this direction as well.