Well, if you want to talk trends, Islam is the only nation that is significantly increasing in numbers. It's the largest religion in the world (I think) and it's definitely growing. Also, the Hajj, which is a Muslim pilgrimage, attracts more people than any other religious site or gathering or rite or pilgrimage. In fact, when Obama was inaugurated, the government called organizers in Saudi Arabia to find out how to deal with so many people (not kidding). So yeah, maybe in 20 years Islam will be the dominant religion, but I guess that can only happen if a nation where Islam is the primary religion becomes a superpower, like America is today (believe it or not, even in our economic woes, we're a dominant nation.) I think 20 years is too little time. I don't think a major change in dominant religions can happen that quickly, because now Christianity, at least in America, is reigning supreme. However, I do think there will be a dramatic rise of atheists and agnostics in the next 20 years. If you think back only 10 or 15 years ago, there were about 1/4 the atheists or agnostics there are now. So yeah, I guess it's hard to say what the dominant religion would be, but I'm certain it has a future.
