This is a nice piece that pulls together some of the different facets related to the story about how American's religion continues to become moralist therapeutic deism - a non-doctrinal and non-institutional approach that is about "what I want it to be." We don't get to choose the moment in history in which we live. The Lord has allotted to us to live in the time of the final devolution of the cultural support for Christianity that has existed since the time of Constantine.
So then, what does this mean? I think it means that we need to be honest and recognize that our numbers will get smaller. The movement of the culture is clear, and orthodox, creedal Christianity is definitely now in a counter-cultural position. The sooner we accept this, the better off we are. Smaller numbers do not mean failure. It just means that God works where and when it pleases him (Augsburg Confession V) and that sometimes believers find themselves at a place and time where only 7,000 haven't bowed their knee to Baal (1 Kings 19:18).
It means that we need to put renewed emphasis on the catechesis that goes on in our midst. The baptized that God has placed in our care must be raised in settings that form them to be counter-cultural people - people have been deeply formed by the Church's culture. And it means that we must continue to speak out with the Gospel because we do have something different. We must set aside all pretense of being familiar and comfortable to the world and stand apart in our baptized uniqueness as we invite others to come and see. Many will reject. But there will be those who recognize something completely different that they have been lacking.