I found that WordPress SE is staying in Beta for more than 4 months! That's an awfully long period.
When it will move out from Beta?
Well, there's no harm in being in public beta, because there are no real restrictions on the site -- it is fully functional.
Generally we look for metrics of "excellent" on the site proposal dashboard before moving a site out of public beta:
http://area51.stackexchange.com/proposals/1500/wordpress-answers
If you'd like to come out sooner, promote the site! Share links to great questions and answers, and generally let other WordPress gurus know about it.
And, as Jan pointed out in a comment -- get out there and vote early and often!