[nikdaheratik]

This is just myopic. The reason why many of those groups have more children is because in any agrarian household, more children = more free labor = more productivity. This can kick in at even a very young age.

In more urban centers, however, more children often means more cost for the family. It has next to nothing to do with religion, and in fact, most of the religious teachings that seem to encourage more fertility are probably just a case of putting the cart before the horse. Those teachings were emphasized because the households that listened to them already had a strong incentive to have more children.

The future, as far as anyone is able to predict, will still have much more urban, educated, and "liberal" people than not, even if those households have fewer children individually. And this will be true so long as we remain an urban rather than an agrarian society.