You're absolutely right that most non-religious people don't ponder the thought. See my response. Christianity won't die out either, you're right, but it will get very, very small, unless something major changes pretty soon. We're at 70% overall, but when you reduce it to just white Christians it goes down to 43%, a minority, and yes, the white part does matter because the actual traditions and beliefs of the denominations are different, due to each denomination developing out of communities that were vastly one race or ethnicity. Under current trends, by 2050, all of Christianity will be a minority in America, and the particularly conservative ones will be a very tiny minority, probably in the teens, or even single digits.
As for non-religious people, they aren't just atheists, and most people who don't believe in God or a god wouldn't even use the term or identify with it, nor the term agnostic. They are, as you say, mostly people who don't give two shits. And as people who don't give two shits, they also won't care if an atheist turns away a Christian, particularly in a future society where non-religion is the norm and Christians are seen as weirdos that still believe in Sky Santa. I'm a Christian myself, and while I don't force my beliefs or biases on others as I'm not an evangelical that feels the need to "witness" to everyone all the time, when the subject does come up and I'm with non-religious folk, I get made fun of a lot, even if they still respect me and hang out with me afterwards. And I'm talking about the "don't give two shits" type. A future full of them would be one where a Christian would feel very awkward expressing his religion in front of them.
As for not being a true atheist if you're "fed up about Christianity and other religions", I challenge you to say that to Richard Dawkins' face. And film it. I want to see his reaction.
Strongly agree with this statement. I grew up in a strong Christian household, and quite honestly I hate the concept of church. I go to a Christian college, and everyone around me feels the need to preach, which to me is stupid considering everyone just basically agrees with the messages they constantly preach. I've just learned to keep my beliefs to myself and just sorta block out the 'Jesus Freaks' as I call them.
As for a decrease in religion, I slightly disagree considering the black population and Latino population are heavily religious. Minus another Great Awakening, I predict it'll drop between the 55-65% range. When it comes to religious followers I ignore race and just look at the percents to see where the religion itself is at.
As for Richard Dawkins, https://www.telegraph.co.uk/news/religion/9102740/Richard-Dawkins-I-cant-be-sure-God-does-not-exist.html . Sure this was a few years back, but the need for him to constantly acknowledge and throw shade towards religion is pathetic to me. People like Dawkins are the reason more religious people don't open up to his ideas.