Will there be a shortage? Will pay increase? Who really knows. The retirement numbers point to a lot of movement, but like others have pointed out, a reduction in frequency in exchange for larger capacity might offset some of the retirements.
I am going to try something crazy for this site and look at some positives. People are traveling at an increased rate every year. The mainline partners are making near record profits despite the high fuel cost. Foreign markets are growing and offering attractive compensation packages to pilots of various levels of experience. There is scheduled attrition averaging over 2000 pilots a year for the next decade. Even with the unfortunate events at Comair, Pinnacle, and Eagle, there has been a large amount of growth at the regional ranks the past 18 months.
This industry has always been hindsight 20/20, it's a gamble on where pay will go. But if you already have your ratings, and are waiting for pay to go up, I would suggest get in ASAP, one of the only constants in this game is seniority is everything.