The recent Pew survey made the rounds.
One can analyze the data from a variety of perspectives. Thankfully, the Pew Research Center allows you to drill down into the survey data.
To some extent the numbers are predictable. The North Eastern US and West Coast have the lowest percentages, as do states with a known libertarian streak. The South and Midwest have a higher percentage of Christians. In all instances, the decline among 18-30 year olds is evident.
What does this bode?
For the immediate future, Christianity is the majority. This said, unaffiliated continues to grow, more so than atheist. The next step is to drill down into the term "unaffiliated." I suspect the consumer culture of the US has an impact. The general "spiritual but not religious" sentiment, particularly along the West Coast, contributes to an eclectic religious praxis. Americans are prone to take what they like from one religion or another, largely for private purposes, without necessarily committing to a religious practice. Which is to say, the rampant New Age spirituality of the 70s and 90s has pretty well settled itself into American culture.
The presence of other religions, while growing, is not exponential. It is to be presumed other religions will invariably be filtered through much of the same consumer spirituality, coming into bouts of conflict with the dominant culture along the way.
Is this end of Christianity in America? Hardly, however, the manner in which religious leaders splice the data will be of importance. Christianity cannot rest on the religious reservoirs in the South and Midwest, nor can it bank on growth through immigration. Christianity must come to terms with its cultural alienation.
Whether Orthodox, Catholic or Protestant, the future of Christianity has less to do with cultural convention, and will be, in large part, comprised of concentrated doses. It was, in my estimation, why the cardinals of the Roman Church rejected the course set by Ratzinger's papacy. Ratzinger had long accepted that the future of Christianity was smaller in size, preceded by a notable period of institutional loss. Attempts to reposition Christianity and reclaim cultural relevance are, perhaps, out of touch with "the signs of the times," and demonstrate a marked refusal to acknowledge the change taking place.