Just to throw a couple more things into the pot for consideration.
There have already been at least two Grammies awarded to Zydeco/Cajun artists. They were Clifton Chenier and Queen Ida. This happened back in the 80's, and I think they were lumped into some non-descipt "folk" category.
I understand some of the misgivings that have been expressed about the new category, and how it might be exploited. However, if the new category had existed then, I think we can be darn sure that Clifton and Ida would have been given their awards in that category rather than in "folk". Perhaps we can gain some reassurances from that?