So what are the plans? When is it coming out of beta?
I don't think the average time it took other languages to come out of beta can be of any indication. Every tree has its own issues and the nature of the language (like flexible syntax) can cause delays.
If I recall correctly, apart from corrections from contributors, it's hitting the mark in (the number of reports filed)/(set period of time) that signals a course is ready to come out of beta. Considering the Greek course was just released for iOS and Android and will undoubtedly attract more users, I'd say hitting that target just moved a bit further away.
Edit: To clarify, I'm a moderator, not a contributor, so I have no inside information on the matter. :)
As has been explained here when a course comes out of Beta is not in the hands of the team. Duo has been unable to obtain data on course responses since there is no access to the comments section and we assume it will need to wait until that problem is resolved. We are also looking forward to its release but of course want to be sure all the bugs are worked out first.