In Holland and Belgium flight schools have this "shortage in xxx years" line in all their brochures for years. Talk with an instructor and his eyes will start shining, euro signs appear in his eyes and he's sure you'll miss the boat if you don't start now spending your floepies now. Probably the same whereever there are flightschools.
In my opinion predicting the growth in passenger seats and future flights is something that is not without a lot of uncertainty, like the economy, stock prices or global warming. About the growth of the low-cost carriers. I ask myself what will happen if there is an accident in the future. (please god let's hope it'll never happen) We pilots won't point our finger immediately towards cost-saving measures but the public will. Hard to say the result but I do think people will prefer to pay a bit more to fly the 'classic' airlines again, resulting in job-losses at the low-cost airlines. By the way I'm not saying this is what's gonna happen, it's just thoughts on these matters.