A classical theme in the sociology of religion is secularisation: the disappearance of religion as such in the modern world, the disintegration of the “sacred canopy” (Berger) or the “disenchantment of the world” (Weber). The secularisation thesis was pretty uncontested until ca. the 1970s, where the New Religious Movements drawing adherents from the counterculture of the 60s and the Iranian Revolution led scholars to question the dogma of disappearing religion.
However, even though religion might be returning, maybe we need to think about what forms of religion are disappearing and what forms remain. The characteristic forms of NRMs in the 60s were rather obscure religions such as the ISKCON (probably better known as the Hare Krishna movement), Transcendental Meditation or something like that. The Iranian revolution marked the upsurge of a more literalist Shia Islam. The Moral Majority of the 1980s wasn’t built on Episcopalianism or Presbyterianism, classic mainline American Protestant denominations; rather, it relied heavily on Evangelicals and Baptists.
Looking at the American or European religious landscapes of today, you notice something odd; the liberal religion of yesterday, the faiths of Tillich or Bultmann seem to be on the wane. The world of the future may be the world of Dawkins and Khomeini, not Tillich or Eisenhower.