We have already seen some decline in religious belief here in the United States, and it seems likely that we will see more in the not too distant future. One of the ways to understand what is happening is to consider how the religious indoctrination of children works. To do so, let's take advantage of the fact that we are in late December and use Christmas traditions as a useful analogy.
Many people enjoy Christmas, in large part, because they have fond memories of Christmas from their childhoods. I am not saying this is the only reason anybody enjoys Christmas as adults, mind you, but I think it is an important one. We often maintain traditions because they are familiar, comfortable, and associated with pleasant memories. Christmas is a great example of that. Even today, there are certain smells that instantly transport me to the kitchen in my family home where Christmas cookies were baked. It should be no surprise that many adults carry on some of the Christmas traditions they remember fondly from their childhoods.
Now imagine how different things might be for children who were raised by parents who did not celebrate Christmas. It isn't that these children might not decide to celebrate Christmas when they grew up. Some might, but I'd guess they would be relatively small in number. And those who did would have a very different experience. They'd be crafting their own traditions that were not connected to fond childhood memories. This would probably result in weaker emotional ties to their celebrations. If enough children were brought up without Christmas, it is not too difficult to imagine fewer and fewer bothering to celebrate it as adults.
Religious traditions probably aren't all that different. I was indoctrinated as a child. Although I would eventually realize I no longer believed in gods and shed most of this indoctrination, there's something important I cannot easily shed: my memories. Regardless of how I feel about them today, the religious traditions to which I was exposed are very familiar to me in a way that other religious traditions cannot be. They helped to shape me. Many religious believers maintain the religious traditions in which they were raised for the same reasons many adults continue some of the Christmas traditions they recall from their childhoods.
When we reach a point where more and more of the "nones" are having families and raising children, we will likely see that these children are raised without religious indoctrination. Even if they are exposed to religious beliefs through the broader culture (which they will be), it is probably safe to assume that they won't be indoctrinated in the way many of us were. As these children grow up, they will be far less likely to have any attachment to religious traditions. This probably means that very few of them would even think to indoctrinate their own children. With fewer and fewer indoctrinated children, we may see a dramatic acceleration in the decline of religious belief.
My family of origin loved Christmas, and I shared this sentiment until my early teen years. At that point, my enjoyment of Christmas began to decline. As an adult, I opted out of the whole thing. It has been well over a decade since I even went through the motions of celebrating Christmas. None of this means I do not still have some emotional soft spots around Christmas that can be triggered at times. But if I were to have had children of my own, there is little question that they would have had a very different experience of Christmas than I did as a child. It is easy to imagine that they might have grown up without much attachment to it. I think the same would be true of religious traditions.
