What would they even give gardevoir?
With all this buzz about ralts being the next CD, is no one asking themselves what it's going to get?
Everyone's hope of a double fairy set wont happen, the only thing I could see happening is future sight, but that would just leave it another pokemon outclassed my mewtwo throw in with the pile of psychic types, it just doesnt seem likely, especially given the patter on only 2 CD's per gen, Bagon and Beldum are guaranteed, and theres no room for ralts
Answers
Bend the rules and give it Fairy Wind.
Retcon Disarming Voice into a fast move.
Dream Eater or Synchronoise as a powerful new psychic move.
Some irrelevant move that nobody cares about.
I don't really care what move it gets, it's not like it suddenly jumps up in meta viability if it gets a fairy fast move. Dragons still outclass it against dragons, Machamp still outclasses it against dark and it's fine against fighting as is.
Using Fairy Wind and Disarming Voice as fast moves would give a lot of fairy pokemon access to a fairy fast most.
Disarming Voice is currently a weak charge move that is only available to unevolved pokemon, Exploud, and Delcatty. No big loss in removing it from those pokemon. Disarming Voice as a fast move with some good stats could even improve Exploud, if they also gave it some halfway decent charge moves.
They could go back and do some other pokemon that were skipped over.
Machop: Machamp with ... Karate Chop?
Geodude: Golem with Rock Slide
Gastly: Gengar with Shadow Claw!
Nidoran: Nidoqueen and Nidoking with Mudslap
Bellsprout: Victreebel with Vine Whip
Oddish: Vileplume and Bellossom... duno
Eevee: Eevee with new charge move Double-Edge, no special move for evolutions
I can't see too many people getting excited for Karate Chop since it's roughly as useable as Counter, maybe slightly less so.
Golem with Rock Slide could be fun, though disappointing coming off the heels of Smack Down Tyranitar.
Shadow Claw Gengar would be very welcome.
The rest... eh.
Reintroducing legacy moves is a fun idea in my book, admittedly in part because the asshurt from legacy elitists after the Body Slam Snorlax announcement was phenomenal. Can't wait to see it again when Shadow Claw Gengar eventually returns!
Why do you think Bagon is inevitable for CD? It still has some scarcity value, so probably too soon to flood the world with Salamence. I think Beldum will happen since its existing moves are two lame to make it a strong player and a new move would be interesting. The moves of Salamence are fine so what would they do to make that better? Give it outrage? If so it would just be another Dragonite and Rayquaza would still be better.
The fact that all Community Day Pokemon have either been starters or current 10k 3-stage hatches it's speculated that Bagon will /eventually/ get one. If it did it likely wouldn't be for a long time.
Odds are the move would be more of a novelty one and less of a straight upgrade, in the same vein as Pikachu with Surf, Dragonite with Draco Meteor, or Ampharos with Dragon Pulse. Having said that I have no idea what move would fit it.