I think if you dig deep enough you'll find that this all-hallowed pilot/instructor shortage thing is often propaganda from the flight training organistations who are now well and truly versed in the art of hoodwinking starry eyed wannabes.
It is just a shame that the vast majority of people who obtain a CPL/IR only find this out through experiencing the 'system'.
I am happy instructing (never thought it would be the role for me!) and to be honest would happily do it for the foreseeable if the work and pay was more secure. As I see it, the only thing going for the airline gig these days is the dosh and depending on your employer that is now an area of contention too. Do you really consider yourself 'employed' as an airline pilot when you pay for your TR, uniform and food? Personally, I'd feel a sense of personal disappointment if I found myself down that route. Seems to me that it's more a case of buying yer way into a dream, something which (through experience) I am no longer willing to do. However, each to their own of course.....