I am not nearly as hopeful as you in thinking that it is an inevitability.
In fact, I see things like this working like a pendulum. Throughout our history (in the US, but elsewhere as well) you swing from a time of a lot of religious support to times of low religious support. And back and forth.
Much of it tied to the things that are happening in the rest of life and society. For instance, the cold war brought renewed faith in the US as the evil communists were sold as being unreligious (so being their enemies, we had to do the opposite). On the flip side, during the Enlightenment when new scientific discoveries were being made left and right, religious power was greatly diminished. Then of course when we are having difficult times like the Great Depression, people tend to look for some kind of help and religion is part of that for many. Again, I think there has been a downward spiral in religiosity in the US overall, but the pendulum can easily swing the other way with the rise of these fascist fucks who are trying to radicalize people and one way is to manipulate religion.