I'll go ahead to use this thread to expand on my thoughts of the dragons.
-Ononokusu: The set up seems clear to me that it should be a Choice Bander. Get in, rape something, get out. Because the fact is that with Dragon Dance, it is STILL outsped by everything this generation, most notably Scarf Flygon. If it opts to SD, Salamence, Sazando, Garchomp, and a host of other attackers have little difficulty shutting it down. Not to mention that its defenses are lacking quite a bit (I believe Swampert's uninvested EQ does 35%-40%).
-Sazando: Lati twins, step aside, THIS is the new Specs abuser. Despite its lower speed and special bulk, Sazando approaches Latios-level SpA and maintains bulk on both sides of the spectrum, not to mention a respectable attack stat. It's weaknesses are much more difficult to capitalize upon, though Blissey is probably more of a full stop thanks to the lack of trick.
-Latias/Latios: When everything is broken, nothing is. Hopefully people will realize that and finally accept these two into OU where they belong (without Soul Dew of course). Their high speed, access to Recover, and wide special movepool all lend themselves perfectly to CM movesets, especially with Sazando taking their Specs niche. Latios will probably want to do something along the lines of CM + 3 Attacks, while Latias can utilize her bulk to do a Sub/CM/Recover/Dragon Pulse bulky set.
-Garchomp: Garchomp will return triumphantly to OU, thrilled to wreak havoc with its draconic brethren. Unlike Ononokusu, who lacks any defensive merit, Chomp is actually quite bulky, and has a trolly base 102 speed (though that isn't so special anymore with the wacky speed tiers around). Swords Dance is the perfect way for it to capitalize on its great type coverage and bulk.
-Flygon: Flygon's niche will remain the same - a nice little scarfer. You would think that Garchomp would overtake it, but I think otherwise. For one, neutrality to all forms of passive damage is a boon to Flygon, and its base 100 speed allows it to deal with the majority of other dragons. We are all aware of U-turn's 4th gen utility right? Now that 156 new pokemon have been added into the mix, scouting will prove crucial to your success, especially with Shadow Tag Shandara/Gochiruzeru, the new offensive behemoths, and other threats flying around in this 5th gen free-for-all.
-Salamence: Salamence didn't like having to take its little trip to Ubers, where it was forced to live under the rule of big brother Rayquaza. He returns to OU to find, surprisingly, more dragons in his place, but he will still rule the Roost when it comes to mixed attacking. No other dragon wields the combination of power and speed that Salamence does, especially with his new ability, Arrogance. Sazando tries to compete but falls short - Garchomp lacks SpA power while the Lati twins can't really do anything too physical. Prepare to face the LO mixed sweeper sets once again folks. Oh, and get ready for something like Garchomp to clean up afterward.
-Dragonite: In the presence of all these dragons eagerly waiting to sweep, Dragonite instead focuses on its bulk to slowly make its presence known. With moves like Thunder Wave, Roost, Agility, and more, Dragonite is more than capable of setting itself up for a slow, devastating sweep. The dream world now grants it a new ability that makes it take less damage the closer it is to 100% health, which creates an additional niche for it. Kanto's original dragon is not to be left out.
-Kurimugan: The defensive dragon, since 77/90/90 mono dragon is awesome. The low speed and SpA don't lend themselves to sweeping, but it could probably be used to sponge particular attacks and retaliate with its 120 Atk. Dragon sports several elemental resistances, all of which are common attacking types.
-Altaria: Ruby and Sapphire's baby dragon is not forgotten. In fact, it will likely be best used filling a support niche on the team. Heal Bell allows it to be an effective cleric and to protect itself from status while boosting its stats with Dragon Dance. It's bulky defenses are always nice, and now that it has Cloud Nine it provides a solid answer to Sun/Sand based teams.
-Kingdra: Johto's dragon seems to fall into obscurity with all these other dragons running around, but that is far from the case. Anyone who has used MixDra in the Rain knows exactly what a terror it can be, and with Drizzle Politoed coming to OU, Kingdra may have many more opportunities to shine. It has excellent all-around bulk, great type coverage, and can even set up Rain for itself if need be, meaning that, unlike other rain sweepers, it doesn't mind having Tyranitar/Abomasnow/Ninetales suddenly switch in. Underestimate it at your own risk.