I would like to know if there is Mongolian coming to duolingo
I absolutely support Mongolian, but I also support jimnicholson's instructions on how to request i.
As of now, no. https://incubator.duolingo.com
Doing a search in the forums on Mongolian AND course is a good way to find some previous discussions.
Mongolian AND course
Please recommend some good sites where I can see what languages are coming to duolingo