Another language suggestion: Pali
I'd like to suggest a language which is hardly known outside of Buddhist groups. Pali is the language of the scriptures of Theravada Buddhism.
I'd like to quote Ominglot.com here.
"Today Pāli is studied mainly by those who wish to read the original Buddhist scriptures, and is frequently chanted in rituals. There are non-religious text in Pāli including historical and medical texts. The main areas where Pāli is studied are Myanmar, Sri Lanka, Thailand, Laos and Cambodia."
Flashcards deLuxe: http://www.flashcardsdeluxe.com
It's a beautiful language; but, I think we'd be more likely to see Sanskrit as it would have broader use and they are so closely related. I imagine they'll work on more dying languages before we focus on dead ones as well, outside of PR moves to bring attention to the project overall.