We can be pretty sure that atheist genes are being strongly selected against, though. That is not something that was nearly as strongly the case in the past. You can thank the pill, and Tinder for that. I suspect that people who are more naturally inclined towards religion will be increasingly dominant in the gene pool as atheists self-select out of parenthood.
The other thing is that religions will be adapting themselves better to modernity and post-modernity. I already see a lot of evidence of this in the beliefs of my young theist friends versus those of gen-X and baby boomer generations. For example, I find that most serious Christians of 50+ are exclusivist, while I find that most serious Christians in their 20s are much more open to the possibility that other religions might also be true.
As a Baha'i, I would say that young people of every religion are being influenced by God's will for this age, and either responding in a positive way (inclusivism) or reacting against it (think ISIS and the like).