These are my guesses from a previous thread, just listing any that I could see it happening to, not necessarily any that I think for sure will. It looks like i was at least correct on the Ralts line so far. Note, I do see the possibility for some dual types to get changed.
Clefairy line(Pure Fairy) Chansey line(Normal/Fairy perhaps?) Vulpix line(Fairy/Fire) Togepi line(replacing Normal for the dual types) Snubull line(Fairy or Normal/Fairy) Misdreavus line(Ghost/Fairy) Mawile(Steel/Fairy) Glalie(Ice/Fairy) Plusle and Minun(Electric/Fairy) Ralts line(Psychic/Fairy) Milotic(Water/Fairy) Whimsicot and Lilligant(Grass/Fairy) Zorua line(Fairy/Dark) Azelf, Uxie, Mesprit(Psychic/Fairy) Mew(Psychic/Fairy) Celebi(Grass/fairy) Jirachi(Steel/Fairy) Manaphy(Water/Fairy) Victini(Fire/Fairy) Newtwo(Psychic/Fairy)