Is there any sense of when we'll be able to leave beta ? I've been watching the stats, and while the number of questions/day bounces around the magic 5.0 mark, all the other markers seem quite strong (and the number of visits/day is steadily increasing).
A site graduates out of beta whenever The Powers That Be™ decide that the site is ready to graduate out of beta. Here's a good post from one of the other beta sites in which a Stack Exchange moderator described how the whole thing works. I will state, though, that increasing visibility, asking solid, relevant questions, providing thorough answers, and generally being highly involved in the site is exactly what we need to do, and (in my opinion) we're doing very well on those fronts. Keep up the good work!
On a related note, though, for what it's worth, there's really not that much of a practical difference between where we are and being out of beta. Graduated sites get a new paint job and elect their own mods (aeismail, Charles, and I are currently serving as Moderators Pro Tempore... you'll get to elect your own mods via public election when we graduate). Other than that, there's nothing magical about being out of beta that makes the site better or anything. Its still up to us—the community—to keep the material relevant and thorough and the participation high.
I'll answer to highlight some of the differences that there are between non-beta and beta sites. For starters, graduated sites can launch promotional operations and get some financial support from Stack Exchange for doing so, while it is much more restricted for sites still in beta. Second, graduated sites get more exposure (e.g., they are linked to in all SE page footers, which increase their search-engine ranking) than beta sites. Thirdly, the customized interface helps somewhat build a specific site identity… very popular sites can even hope for more of that (see how Gaming.SE became Arqade).
Finally, there is at least one drawback to graduating too early: rep levels for privileges are higher, which means upon graduation a lot of regulars will loose their mod-like powers (which can lead to more work for the mod team).
Regarding the timing, traffic still needs to improve (both in term of page views and question rate). It is growing quite slowly (check our stats), so we'll get there eventually. But organic growth is good, it gives the community time to create the best site possible.
So, while I hope Academia will soon graduate, I wouldn't hold my breath… but that's not a bad thing.
I don't really understand the difference between beta/not beta, but it seems to me that our questions per day is still on the low side. I think if we want to encourage repeat visits by people willing to answer questions, we need more questions. I also think we need to discuss delete/close/off topic issues a little more than we do (possibly in chat). Finally, the our tags still need a little work. I don't know if any of these things will directly lead to graduation, but I think they would help the site.
As for when, I am guessing on our beta birthday.