I think the first challenge will not be finding pilots for the majors, but finding pilots for the regionals. Somehow, the majors will have to figure out how to make the regional jobs attractive enough, or THEIR regional pilot jobs more attractive than their competitors, to attract enough butts to fill seats. I don't think doubling first year pay will help very much.
I believe, at some point in the very near future, one of the majors will decide that putting the pilots of all of their branded flights at the mothership will do the most to attract pilots. Their are tens of thousands of foreign pilots that would love to work for UAL or DAL. But they would not come here to work for Mesa.
At the moment, we are probably trending this way anyway. Scrapping the 37-50 seaters, and buying more narrow bodies is moving the bar that way.
We will see how the end game plays out over the next couple of years.