I don't think that we can really dethrone dragons and steels as the kings of OU. Dragon is hands down the best typing in the game, even on paper. It sports useful resists and itself is only resisted by one type,steels. Combine this with the fact that every one of them is a 600 base stat behemoth and it is pretty obvious why they run OU.
Now, the single best way to handle these dragons is steel types, and that is because they can actually take a dragon type attack. Ice types, with or without SR, just cant come in repeatedly on Outrages. At most they can attempt a revenge kill, but i think weavile has that niche on lockdown. If we want to remove dragons from the limelight, our pokemon must be a steel type, but i don"t really know how another steel type can successfully popularize a lesser used typing when the other dozen steel types have failed to do so.
On a different note, i think one thing that we need to consider while deciding which type to raise up is which individual pokemon are we planning on raising up. For example, we may find a hundred good things about bug typing, but at the end of the day, most bug type pokemon kinda suck. Almost all of them are saved by their second typing (think scizor, heracross), and i really don't really see a way to bring things like Garvantula up to an OU level even if we create a pokemon that instantly removes stealth rocks on entry. This is also my main problem with trying to save grass typing: the only grass pokemon that are really OU viable on a macroscopic scale are Shaymin, Roserade, and Virizion, and even there Shaymin is a stretch. I really think we need to take a hard look at the pokemon we are trying to lift up instead of just talking about typings in general.
Now, in my opinion,i think our best bet would be try to nuetar fighting types and lift up dark types. I think the main thing fighting types have going for them is that they can bash the shit out of the main defensive typing (steel) and there really aren't too many OU mons designed to take strong physical fighting attacks (most paychics ar e more specially defensive). I think if we make a physically bulky mon that can stomach fighting blows, i think we can bring the fighting type down a notch. Plus, if we manage to reign in the fighting parade, there are a plenty of dark types just one tier down itching for a shot at OU. Things like Sharpedo, Honchkrow, Scrafty, and Weavile come to mind immediately, but things like Bisharp and Krookadile may also see the light of day. . Even within OU, Hydreigon may see a sizeable boost in usage if it doesnt have to duck around close combats all the time. Dark typing would be a fine choice for this concept.
Bring up Dark, bring down Fighting
Did You Stand Too Close To The Fire?