Do we have a plan to incorporate the Bengali language in Duolingo in future?
I hope so! I'd love to learn Bengali. After all, it is one of the most widely spoken languages in the world. Maybe we'll see an incubator team soon :)
Edit: There is an incubator page up, so at least there are plans for it sometime! http://incubator.duolingo.com/courses/en/bn/status