[skissane]

I think the future of religion in the West – and eventually probably much of the rest of the world as well – is countercultural (ultra-)conservatives such as ultra-Orthodox Jews (Hasidim and Haredim), the Amish, conservative Roman Catholic groups such as traditionalists (SSPX/etc) and Opus Dei, Quiverfull Protestants, Salafist Muslims, etc.

Many of those groups (1) have high birth rates (large families starting at a young age), (2) have high retention rates (>80%, sometimes even >90%) generation after generation. There is no good reason to suppose that (1) or (2) are going to stop any time soon, and even they do for some of them, they are unlikely to do so for all.

I don't think we should expect these groups to follow the same secularising trajectory as mainstream religion. These groups have evolved a cultural immunity to the temptation of defecting to secular modernity which the religious mainstream failed to evolve.