Comment by kpil

I think the current estimate is that there are almost a half a billion more Christians than Muslims (in 2025.)

One reason is that the number of Christians in Sub-Saharan Africa is growing. But extrapolating the trends, yes Islam will probably become the largest religion in the coming decades.

Or at least maybe - looking at birth rates, it seems as second generation muslim immigrants to Western countries have even lower birth rates than the native population. That might happen also in regions say like Pakistan and Indonesia and other fast growing regions, depending on economical or other changes.