I think one of things being overlooked here is that what most players struggle with is not understanding basic poker concepts, but rather implementing them rigorously and with absolute discipline. If you can do that you will probably always make money, even as games get a bit tighter and worse (in terms of bad play).
The people who may suffer if things dry up a bit are those who play well sometimes but are streaky and prone to tilt. These will be the people that the better players make their money off of (the new fish). Right now, fish are composed off complete ignoramuses and also those who are tilting. In the future most of the complete ignoramuses will be a thing of the past. The rising waters lift all boats and there is a basic poker education that is occuring.
At the same time, the more refined you get conceptually and the more disciplined you get, the more you improve relative to the general populace. Just like athletes are more "athletic" and generally "better" than those in the past, it comes down to the same thing.

-g