On this forum we have endless discussions about immigrants and especially immigrants from islamic countries. Islam is undoubtedly the fastest growing religion in the world. Not because it would appeal to really anybody who isn't a muslim, quite on the contrary, but because of the higher birth-rates of muslims.
However, despite that, whenever there are questions about people's religion the fastest growing category is the "no religion"-category. I sincerely believe that all the doom-mongering about this and that European country becoming a muslim-majority country by the year 2050 or even earlier, will turn out to be rubbish. It is more likely that "no religion" will become the majority in most countries by that time.
Which by no means is not a bad thing.