This site has been online for a while now, and is very active, but it's still in beta.
Shouldn't this site be made an official part of the stackexchange?
The simple answer is We don't know.
The powers that be (read: the employees of SE) have the final say as to when a site graduates from beta and it seems that the 90 days is more of a measure to keep the site or let it continue on.
The fact that we made it this far tells me that they do want us to graduate. As to when, only the SE team themselves can answer that.
This blog post covers the basic process of evaluating a site for graduation:
Here's another blog post that's not quite as relevant to this discussion, but it offers another take on the statistics involved:
Does this site have a chance of succeeding?
But more specifically to this site; you're doing very well overall. When we evaluate a site for graduation (and the "lock in" that entails), we want to be sure there is a consistency in both its growth and quality that will all-but-assure its long term success.
You're showing a pretty strong pattern of growth in overall viewership. I don't see that stalling anytime soon. Two things of note (for the sake of completeness) — the retention of new users (after those spikes) isn't too hot. That's not necessarily a problem, but it could indicate a lower quality and interest in the site overall. I don't think that's the case here.
Also of note, while voting seems pretty strong, there aren't that many high rep users for its size. That could show a lack of a really strong core, central community, but (again) seems like nothing to be particularly worried about.
Here; I'd be happy to share the rest of my written evaluation verbatim. This isn't to cause concern or debate, but just to give you a bit of transparency about what we're looking for on our end —
The strong evalation participation from the community was helpful and the quality looks strong overall. It's nice to see moderators actually take action when a question evaluates poorly. That's unusual (but good).
I noticed the same thing as [the others]. Seems a bit odd that one answer is good enough the majority of the time. Could be that those answers are so awesome, nothing further needs to be said. But could also indicate a "quiz show" mentality… that there's perhaps too little make-it-better ethos. Users are more apt to get their basic answer and move on than on most sites of this type. Little editing and few multi-answer posts. I'm surprised there's NOT more vying for top movie critic/philosopher, given how prevalent that is in pop culture.
Graduation: Not yet.
It's getting there but this site could use a few more evaluations to show a solid track record. Based on the breadth of the subject, this site should be growing past those higher-visitor roles before graduating.