The retirements will have to exceed the legacy airlines' rates of shrinkage, consolidation and outsourcing of their work. Nobody trumpets these figures, but at most majors the seniority lists are 40% off their peak numbers. Graph it out and you'll see retirements are not replaced on a 1 to 1 basis.
With fuel price volatility (and government making it worse by adding carbon tax schemes) I'd hope for, but not count on, a hiring wave.