How About a Lang Belta/Belter Creole Course (from "The Expanse")
The creole language for denizens of the Belt in the show "The Expanse" was created by linguist/polyglot Nick Farmer. It's a real, functional creole language, and there are quite a few people actively studying it in various communities online and IRL right now.
A question that keeps coming up in those communities is: "Will there be a Duolingo course? And if so, when?" So, how can we make this a reality?
Get in the line.
I will say however that this seems extremely unlikely on short scale. I don't know what's "quite a few" as I had never even heard of this but seeing how people have applied for actual real world languages with millions of speakers and huge demand such as Arabic, Serbo-Croatian, Afrikaans, Finnish etc. and Latin that are yet to be added, I don't see why this (especially a Creole) would be a priority. They do do publicity stunts like High V and Klingon so my best advice is to make Expanse as popular as Star Trek, The Game of Thrones or LoTR and maybe then you have a shot.
I'm not sure why you're getting downvotes. People, let's not discourage investment and interest in the Duolingo platform, OK? If you don't appreciate, desire, or understand the request, just move on. :)
That being said, I would love a Lang Belta course on Duolingo, and I know some people who would be interested in Duo solely for the ability to practice Belter Creole. I agree with @Maclomhair; Nick Farmer and the authors of The Expanse would probably have to get involved.
For now, there's a Memrise course: https://www.memrise.com/course/1476694/lang-belta-belter-creole-phrasebook/
I gotta agree with other posters that this will be wayyyy down the line for Duo, after many real languages, Elf, Dothraki and probably other conlangs https://en.wikipedia.org/wiki/List_of_constructed_languages#Artistic/fictional_languages By which time the franchise will be long done.
Unless of course, the show grows bigger. The book writers do take advice from GRRM but doesn't seem the popularity of GoT has quite rubbed off on it :|