I make it more than sixty years before we start to get close to being a majority in the USA (and I'll be in my early hundreds if I live that long), but I can reasonably hope to live to see outright atheists making up 20% of the US population (30-40 years from now, optimistically). I think the internet is going to drive a faster change than occurred in Europe, now that the trend has started. And that's a big enough minority for atheists to get all the consideration they could reasonably want, I think. Everyone will know atheists and most atheists will be 'out'. Stereotypes will be hard to support beause so many people will have first-hand knowledge of how diverse we are. Theists will change too, and become largely less fundamentalist, reducing the tension between atheists and theists considerably. Groups focused around atheist solidarity will fade as they become unnecessary: atheists won't need that kind of help anymore to find people who don't have a problem with their atheism. And major Christian denominations will be happy to have atheists as members, just as they're coming to grips with including gays. And that's what will slow down the rise of atheism in the USA: when a Christian family can take their atheist kid to church without him or her having to pretend to believe things they don't and having a preacher tell them things about atheists and evolution they know aren't true or their parents being hateful to them for not believing all the same things they do, churches will reduce their production of atheists considerably.
I'm not anti-Christian. I'm anti-stupid.


