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All the pokemon in "no doubt" have already been confirmed or are incredibly obvious like clefairy and togepi lines.
-Pikachu line is one of the most obvious ones in my opinion for a number of reasons; pikachu has been buffed in every generation (lightball@gen2, volt tackle@gen 3, lightball buff@gen 4, lightningrod@gen 5), he is in fairy egg group and his gen 2 counterpart (marill) was confirmed fairy.
-Dunsparce looks like a fairy type and needs the fairy type.
-Celebi is as close as a fairy as you get in Pokemon, the only reason he is not in "no doubt" is that he needs to lose the psychic type to become fairy.
-Volbeat/illumise, same as above, those things look like fairies.
-Snorunt is an ice fairy, Glalie, well, it's its evo.
-Audino and Meloetta are also very likely.
All the pokemon in "good chance" also have very good chance of becoming fairies, but unlike the ones above they don't look as fairy-like.
Finally the ones in "maybe" all have qualities that make them candidates, but there is no telling how many or if any of them will become fairies.