Well as far as I know, the park signs and the Disney World website still refer to it as "Disney-MGM Studios". I don't know if that will be changing- maybe they're very gradually trying to change it over, although to me the official change would be when they change the park signs and references in pamphlets and websites. To me Disney-MGM Studios makes more sense than The Disney Studios, since Disney fired all the animators, and there is no working animation studio there anymore, but in contrast there are plenty of references to MGM movies in the Great Movie Ride and other attractions.