Taken from the same source of your description:
Religious scholars generally agree that writing a single definition that applies to all religions is difficult or even impossible, because all people examine religion with some kind of critical eye, and the term is therefore fraught with ideological consequences for anyone who might want to construct a universal definition. Talal Asad writes that "there cannot be a universal definition of religion ... because that definition is itself the historical product of discursive processes"
So, no, you can't really define religion.
USA courts legally ruled that it was a religion, though, and I'm sure they debated for days about it.
"Up is down, and atheism, the antithesis of religion, is religion," said Fahling.
The Supreme Court has said a religion need not be based on a belief in the existence of a supreme being. In the 1961 case of Torcaso v. Watkins, the court described "secular humanism" as a religion.
Not the point though. I meant to say that it's become an increasingly organized set of beliefs. There's a point in every religion where it moves from an oppressed group of people who believe the same thing into a large, accepted organization, and that's what's happening.
It will be a religion when:
1. They create a proper symbol for atheism.
2. They create a ritualistic set of actions, like monthly meetings/debates.
3. Someone tells atheists what to do and what to believe, and nobody questions him/her.