I do not believe in any sort of gods, and this makes me an atheist. By itself, being an atheist does not compel any sort of action on my part. The fact of my atheism tells you something about what I do not believe but virtually nothing about how I live my life.
When my atheism is combined with my beliefs in the importance of civil rights and awareness of public attitudes toward atheists, it makes sense to discover that I am motivated to promote atheism as a civil rights issue. Similarly, when my atheism is combined with my conviction that theistic belief (i.e., that some sort of god or gods exist) is harmful to society, it makes sense that I am motivated to speak out against religion, work to reduce its influence, etc. And yet, I would welcome no longer having to think of such matters. Life after atheism sounds pretty good.
Life after atheism would be possible in a post-theistic society. There would no longer be any need to discuss atheism because it would be the norm. Atheist civil rights would be taken for granted in much the same way that the civil rights of White men are today. Anti-theism would make about as much sense as "anti-unicornism" in that there would be no need for it at all.
Children would learn about Christianity and other religions in history books in the same way they learn about other institutions that are no longer with us (e.g., slavery). "Why did it take people so long to realize that none of that stuff was true," they would ask their parents in reference to religious belief.
Atheists who are now occupied with promoting atheist civil rights and opposing religious extremism could involve themselves in other matters. Plenty of problems would remain, and effort would be required to address them. Atheists would be freed from the burden of having to fight for the bigotry and discrimination we face and better able to work on solving other problems.
I don't expect to experience life after atheism during my lifetime. I wish I could be more optimistic about that, but the disease of religious belief has proven to be surprisingly resilient. I can only hope that future generations will get to live without religion. And of course, I can keep working in the present to make progress in that direction.