All rests with Togekiss
The hopes of fairy types kinda lives or dies with togekiss. Gardevoirs kind of an odd case, is the best fairy attacker for similar reasons to why dragonite is the best nonlegend flying type, high stats and lack of decent stat competition. It's also so.ewhat glamorized as a fairy attacker vs machamp because confusions huge power and also effective against fighting. Gardevoir lags noticeably against Dragon types and dark type as a result, and it seems like unless fairy wind is a fast move, and is given to Togekiss, there might not be a use for fairy outside of machamp, and if they hold off till sylveon for fairy wind, the usage of fairy will have long since passed, as well as sylveon being tank in stats but being less so than Togekiss, and having noticeably lower attack than Togekiss as well.
I hope they give it something, most of us likely have been preparing our togepi for Togekiss for some time now, and it is probably one of the most anticipated gen 4 evolutions.
Answers
They didn't plan out fast/charge move distributions very well when the game started. They need to retire some charge moves and make new fast moves out of them. Disarming Voice is a worthless charge move, but would be an incredible gain as a fast move. With Disarming Voice and Fairy Wind as fast moves, most fairy pokemon would be able to have a fairy fast move.
I wouldn't put much stock in them do I g that for disarming voice, there's no precedent for it, and likely it would put gardevoir ahead of all ofther fairy types by a mile if it got disarming voice as a fast move, likely there wouldn't be any fairy type that could compete until Xerneas, niantic seems to want to keep things able to be outclassed
A lack of precedent isn't reason enough to rule out the possibility of something. Evolution items were missing from Gen 1 and were added to Gen 2, for example. Lack of immediate competition isn't quite reason enough either. Unless incoming stat changes say otherwise Kyogre*, Groudon, and Psychic Mewtwo are the undisputed champs of their respective types across all generations. Fairy is a pretty niche type, it's not like a dual fairy Gardevoir will be game breaking.
EDIT: After hitting submit I remembered we'll be facing Palkia soon-ish and that starters with community day moves will be a thing that could eventually rival Kyogre. Depending on how megs/Primals are added, P-Kyogre will likely remain the undisputed water type king. At worst it would momentarily lose the crown only to regain it later.
Those legendaries will likely be outclassed by raid day version of themselves with exclusive moves, or.mewtwo could get threatened by some of the gen 7 Mon if they have better moves, particularly ultra necrozma of gen 4.giratina ias a ghost attacker if shadow force is added, but that is a long ways away, as well as palkia is an immediate threat to kyogre if given a water fast move, as well as groudon from some ground types, and rayquaza from the sinnoh dragons if their signature moves are added
Never said dual fairy gardevoir would be, but non dual fairy is more or less the most extreme specialist there is.
There's a difference between not having evolution items and changing a charge move to a fast move
