One last thing (how many times have I said that) that is tremendously important to consider:
Since the dawn of modernity, great thinkers have predicted the impending demise of religion. Popular in sociology more than 100 years ago was secularization theory. Much as is being argued here, the theory predicted that as people got smarter and smarter that religious belief would decline, particularly in the public sphere. Peter Berger is a very notable sociologist who has argued that instead of secularization in modernity, you see pluralism: people go a little post-modernist and lean towards the perspective that every religion is, in some sense, equally valid, and often these folk believe that a fundamental problem with any particular religion will be group X who "pervert" what religion is really about ("and aren't we all after the same thing?").
The polling on religious numbers can be very misleading. I tend to agree with those who argue that the number of real atheists isn't increasing significantly; rather, the way the questions are asked combined with the type of impression a person would like to give ends up lumping a lot of "disenfranchised believers" into the non-religious category (because that person might choose not to identify with a particular church). In the US, for example, the number of atheists has been stuck at 5-6% for a while.