This actually is a good idea but one I don't see will happen this year.
At the moment, there are only a few users on Musing. If people start asking in a different language, then you are basically cutting half(or even more than half) of the possible answers you will get. Others will also just "Google Translate" an answer they found in Quora or Yahoo Answers as this approach is hard to keep track.
There is also the issue of hiring many curators (one for Spanish, Indonesian, Russian, French, Malaysian, Japanese, etc..) which requires a lot of trust between the curator and the one who made Musing.
With English as the main language being used in this platform, a lot of people could ensure and visibly see that questions and answers upvoted by Musing are all of-quality and not plagiarized.