As I've said before, it is highly unlikely that the development team will retcon present typings of already existing Pokemon, since it's been established in almost every Pokemon medium that all Pokemon are of specific typings. Altaria exists as Gym Leader Winona's signature Pokemon, and has been established multiple times as a Flying-type in the games (especially the PWT in BW2) and anime (Fortree city battle). The same pretty much applied to the addition of Steel-types in Generation II, where there were no pure Steel-types introduced from Kanto, and Magnemite's family was given an additional Steel-typing.