A good post on the future of religion can be found at http://blogfutureblog.blogspot.com/2011/03/future-religiosity.html. The author argues that factors working in favour of religion are
1. Religious people have more children than non-believers and will pass their beliefs down to their children.
2. Religious people will tend to listen to programmes which confirm them in their convictions while avoiding those which challenge their beliefs.
The author identifies the factors working against religion as being the easy availibility of alternative viewpoints (for example via the internet) and the fact that many young people will explore alternative perspectives online which will lead to them being exposed to secular opinions.
As regards religious people having more children than non-believers this may well be the case for the Mormon and Islamic communities to which the author refers. However although the official teaching of the Roman Catholic Church is that contraception is wrong, in practice many practicing Catholics disregard this tenet of Catholicism and use birth control (witness the fact that many Catholic families, particularly in the developed world have only 1-2 children).