I believe that there will never be a pilot shortage. I agree with a poster above that there were a lack of willing applicants in 2007 to work for such low wages. We will only see a shortage if ATP minimums are required for part 121 work.
I think we will see a lot of the majors absorb some of those retirement numbers in the future and with most having a thousand or more pilots on the street, it will be a long time before the majors will need to hire off the street. When they do, regional pilots will be competing with military guys and others from part 135 and other defunct 121 carriers.
The days of getting on with a regional and upgrading in 2-3 years are over. We need to secure contracts with decent work rules and livable pay for FO's because in some cases it will be 5-10 years or more to upgrade. Regionals are becoming career destinations for some of us whether we like or not. The opportunities for advancement are no longer there.
I may sound like a pessimist, and maybe I am bitter to some degree, but this is real and we should not get our hopes up over some major airline retirement numbers without looking at the big picture.