I think steel attacks will eventually kind of die down. As of now fairy is used a lot because it's new and it defeats obe of the most OP types i gen 5, but I think we will eventually see a reduction in use of fairies and OU will probably limit itself to having Mega Gardevoir, Mega Mawile, Azumarill, Florges and maybe Klefki or Carbink, though I doubt Carbink will be higher than RU and I have a feeling Klefki is goin to be UU. If you take a look at those pokemon, Azumarill, Mawile and Klefki aren't weak to steel. Carbink is x4 weak, but he will probabaly only have a small niche in OU so we won't be seeing much of it. Sure, steel attacks will be more common than in gen 5, but in gen 5 we pretty much only saw iron head on Jirachi and flash cannon on Magnezone. I think Aurorus will find more use once the metagame will balance itself out.
Also, we can't forget that fighting has gained a new weakness which will make it much less useful. I actually think that ghost type usage will be the type that gets the biggest jump, as it now has perfect neutral coverage with the exception of dark and normal which can be remefied with focus blast or brick break.
In conclusion, I wouldn't write off Aurorus right away, as it can find its use, as like Haka was saying, most of Aurorus' weaknesses are more physical based, so with smart switching you can gain momentum by switching a pokemon like, say, Chandelure on a fighting or Steel move or Salamence on a ground move. Even if the "skilled" smogon battlers don't use it, I can see it be used properly, as I think the battlers with the most skill are the ones who can make mediocre pokemon shine, not the ones that copy and paste pokemon and movepools off of the smogon website.
On another note, what do you guys think will happen to Jirachi now that it's weak to dark and ghost?