This thing will pretty much be only used to lure in Thundurus-T, like jrrrrrrr said, and to use a fast hurricane.
This thing did have the potential to be awesome (the 121 speed stat speaks for itself), but the nerf to special attack by 15 is very, VERY noticeable. Say you switch in this thing as a quickfire terrakion check, like Tornadus-I (normal Tornadus) did. From a Tornadus-I, you've got the OHKO, courtesy of its monstrous 125 Sp.A stat. People will try this strategy with Tornadus-T, only to find the Terrakion gets away with a 2HKO, and retaliates with a STAB Stone Edge. You've now got a dead Tornadus-T. You may be able to slap some Specs on it to maim Terrakion, but flying-resists and walls are hardly rare with Chansey, Tyranitar, Jirachi, Heatran and Rotom-W round every corner. It completely crumples to VoltTurn teams and Rotom-W and Scizor don't help its case.
People may think 'Oh, improved defences and Regenerator!' but 79/80/90 defences don't exactly scream out 'Bulky Attacker' as any super effective hit destroys it, and with Thunders, Ice Beams and Stone Edges constantly thrown around the tier, as well as the fact that either a Rotom-W or Thundurus-T is on every rain team, and Tyranitar is all over the place, this thing may have had potential, but the tier has all the Pokemon bar Zapdos that make Tornadus-T scream, and as if all that wasn't enough, sun teams are starting to see more appreciation, cutting Hurricane's accuracy and bringing Heatran along with that, and more and more viable Stealth Rock users are coming around.
This thing will pretty much only see use to get rid of Contrary Serperior when it comes out and will probably go down to UU, a tier that actually suits its needs or just in BL for the rest of B/W/2