At this point, they require you to have your ATP mins+ written, so you're ready to take your ATP check ride on day 1 of your class; you just need to learn the airplane.

If it becomes too difficult to find qualified people, they would likely drop the ATP written requirement (since the new additional training is a prerequisite to taking your written), provide the new additional training, and provide you an opportunity to take the written test. Before the normal airline training begins.

This would amount to a large expense on airlines, however they would pretty much need to if no one can afford the new training to even get as far as taking their written.

Make sense?