I don't think this will cause a shortage of pilots, but what it will cause is the 121 candidates to be more experienced and more dedicated. 2 years ago any flight school could tell a student that they would be airline pilots in as little as X months. Any person with the money who likes airplanes could become an airline pilot.

I think 1500 hrs is a higher barrier than most might think. Those who graduated in '02-'04, remember how many of your classmates went into different fields instead of putting in the time grinding as a CFI? When you actually have to work to become an airline pilot, I believe the candidates will be more dedicated and experienced.