Religion is pretty much a cultural universal. That is to say, no human culture is without one. So if Christianity disappears in the West, we can expect other religions to rush into the void. And those religions, say some observers, are likely to be a version of those that human cultures have turned to around the world and long before Christianity took hold. In other words, they will be “pagan” religions.
Other major religions today, such as Islam and Judaism, are also very different from paganism, and they have similar concerns with Christians about the prospect of its revival.