In The Christian Science Monitor, Michael Spencer predicts a massive collapse of evangelical Christianity within ten years. "Within two generations, evangelicalism will be a house deserted of half its occupants." And it gets worse.
According to Spencer, there are a few reasons for evangelicalism's dire prospects. Evangelicals focused too much on the culture war, and didn't spend enough time on promoting a compelling theology. And the only thriving churches are "megachurches."
Ironically, the billions of dollars we've spent on youth ministers, Christian music, publishing, and media has produced a culture of young Christians who know next to nothing about their own faith except how they feel about it. Our young people have deep beliefs about the culture war, but do not know why they should obey scripture, the essentials of theology, or the experience of spiritual discipline and community. Coming generations of Christians are going to be monumentally ignorant and unprepared for culture-wide pressures.
But meanwhile, there's going to be a rising tide of secularism as our culture becomes more "religiously antagonistic" and "Intolerance of Christianity will rise to levels many of us have not believed possible in our lifetimes, and public policy will become hostile to evangelical Christianity, seeing it as the opponent of the common good." The biggest beneficaries of evangelicalism's downfall, however, will be Orthodox and Catholic churches, which can offer more doctrinal underpinnings and a long history. The whole article is worth reading, as is the commentary on it at BeliefNet.