I've been thinking about this recently. In the past when we couldn't explain things, we attributed it to a god of some kind. There were many on offer, to explain thunder, sunrise and so on. Now we're left with just a few that people still believe in, one that started it all off or helped guide human development- the monotheistic god.
Science is showing us (and humans are taking notice, little by little) that we don't need any god to explain what we see around us.
But seeing as so many people want/need to believe in something greater than themselves, I wonder if the religions like Scientology and Raelian will end up being the dominant ones in a few hundred years. People will have faith in aliens, rather than gods.
It's too early to say for sure, but it seems a plausible idea to me. Religions change with the times. If god belief is on the way out, could humans feel comfortable without any higher power to look up to (as I hope will happen), or will alien religions move in to the spaces left by their demise?