This bleak but interesting article from Micheal Spencer author of the internetmonk blog argues that Evangelical Christianity has become too culturally compromised in the United States and will therefore fade out as a movement of any significance over the next few decades.
However should I temper that pessimism with this article from TIME magazine about how Calvinism is growing in significance in the United States.
Although in 1947 it seems this article also from TIME heralded a Calvinistic come back. Maybe it waxes and wanes?