Hi, I'm a student of Arabic and I'd love to incorporate the Duolingo method into my studies regularly. Are you planning for that in the future?
Judging from the May 2013 discussion (and some previous answers given by the team), they won't add any new languages themselves, but will introduce a system for the users to add new languages. This will probably come this year.
I wouldn't see Arabic being too far off. However, I would imagine the reason why it isn't up right now is because of a lack of Arabic experts working with Duolingo.
I know a lot of Arabic experts though I think it's because it's not a Latin language so maybe there will be technical challenges to add Arabic just like Chinese to Duolingo. though in general this is already really not bad at all, this site is amazing!