Nobody is irreplaceable. As the number of subspecialty grads will increase (the same way anesthesia grad numbers have), AMCs will pick and choose the suckers they need. As long as we don't have a numerus clausus in place, it will only get better for them and worse for us. This is not doom and gloom, just simple market economy. See what happened to practicing law.
The only way to prevent this is to have very strong roots in the hospital/OR, so that the surgeons complain if they get a faceless drone instead of a specific anesthesiologist. I can see subspecialty-level relationships being a great advantage, especially in a private surgical setting. If the surgeons are employed they can complain all they want, if the hospital stands to gain money by changing the anesthesia group.