Ok... let's see every single Competitive Fairy (in my point of view of course)
Clefable: Now this poke actually does have some nice resistances instead of a ridiculous Immunity to Ghost, and now have a true STAB to wreck havoc (I'm Absolutely sure that this thing it's going to have Moonblast). Also it's Special attack got a Buff and with Calm Mind, Magic Ward and Unaware (the last one i'm just taking it from Serebii) we have a huge UU poké threat at least...
Wigglytuff: NO... this i don't really think that this one can get even out of NU...
Mr Mime: If this thing can have Technician + Draining Kiss, maybe we can have a nasty Sp Defensive Fairy... Psychic Type it's going to scare Poison Types out and HP Fighting can get a nice power because of Technician. Probably can get into RU since it's really outclassed by Mega Gardy.
Azumarill: Actually this one can be a good OU poke. Water type has always been a nice type, and paired with Fairy only gives one more Weakness and adds 3 resistances and one immunity. Yep it's really sluggish but i think it should be able to deal with the dragons if you manage to switch in safely.
Granbull: It's outclassed heavily by Azumarill so, probably it's going to be one or two tiers lower than it... So, expect RU at best.
Gardevoir: This one it's going to have a really huge support in OU since it got the tools to a huge success... Mega Evolution - Strong STABS - Nice Coverage. I Can see a good usage of Metagross with Meteor Mash or Jirachi with Iron Head just to beat MegaGardy, even with those two new weakneses Probably OU as well but it's low Physical Bulk and relatively mediocre speed, it's going to prevent that thing from going further.
Mawile: This is another one that can be seen in OU since having the HIGHEST NON BOOSTED ATTACK IN THE GAME it's something, and it does have a nice bulk, even with that poor HP, since it can intimidate in the switch and then getting it's Mega Evolution. Also, even unSTABed, Sucker Punch it's going to deal with a LOT of pokémons that normally can handle it.
Togekiss: I really hope this one can get a little bit more speed... If get at least 90 Base Speed, this is going to be the best Fairy Outside of ubers, since now it does have more resistances, and also have all the tools to be a demon...
Whimsicott: Now this one have more resistances in exchange of that 4x weakness to Poison. I think it's going to be even more annoying but is not going to be a really huge force outside of the thing that we already know of it. RU or UU at best.
Florges: It's similar to Gardevoir but doesn't have mega evolution, have less Speed and less Special Attack in exchange for a little more physical Bulk and a lot more of Special Bulk... But the really bad part is that this poke doesn't have a nice movepool. It does have Wish but i can't see any other usefull support move and it's attacking options are only Grass and Fairy Type Attacks, so we have a Lilligant without Sleep Powder, Own Tempo to Spam Petal Dance or Chlorophyll to have an amazing speed in sun and doesn't even get Quiver Dance. So this one it's probably going to be a really huge force in NU replacing Gardevoir unless it got a bunch of options by breeding.
Aromatisse: Do you remember about a poké named Musharna? Give it a new name a new type, a little bit less bulk, some other coverage moves and no direct Recovery and you are going to get this one... Also... you remember which Tier it's Musharna? Yes, Aromatisse it's also going to that tier...
Slurpuff: This one it's like a mini Clefable, so probably it's going to be played like it in RU now that we can expect Clefable in UU. Also, Unburden can be nice to patch that mediocre speed.
Sylveon: Many people thinks that this one it's going to have a huge success and i think they are a little bit wrong. Sylveon it's really like a Vaporeon but with less physical bulk and no ways to patch it (Vaporeon have two ways in Acid Armor and Scald Burns which can from a STAB Move). I think it's going to be a nice addition to UU.
Dedenne: Really? are you expecting me to say something about this? forget it...
Carbink: It's similar to Deoxys D but with less attacking stats (which include speed) and a not so hot Supporting movepool (at least it got SR). Maybe can be played with Sandstream support to became annoying to bring down specially and racking passive damage with SR, Toxic and Sandstorm. Even with that, i think isn't going to be higher than RU.
Klefki: Who cares about not having a huge speed when you have nice bulk, a nice Defensive Typing and Prankster which can let you get a Calm Mind, a Thunder Wave, a Sub or some Spikes without barely any problems? We can expect this one to be in UU or OU...
So, my prediction is:
1.- Mega Gardy
2.- Togekiss
3.- Mega Mawile
4.- Azumarill
5.- Clefable / Sylveon / Klefki
8.- Whimsicott
9.- Slurpuff
10.- Carbink
11.- Mr Mime
12.- Florges / Togetic
13.- Aromatisse
14.- Granbull
15.- Wigglytuff / Dedenne
If Togekiss got the Extra Speed, you are free to swap it's place with Mega Gardy... Why? Timid 90 Base it's going to be a huge boon, being able to speed tie or outspeed at least some pokes like non Mega Lucario, the Slower Ubers, Heracross, and getting the upper hand on many usually Adamant and Modest Dragons like Hydreigon and Haxorus.
Cya!!!