It's actually impossible to tell at this point. We don't know what we'll get in Gen 5, a bunch of other OU pokemon that nerf it? What if it's speed stat is horrendous? We just don't know. There are so many factors out there that have to be determined.
Garchomp was uber because it had that perfect recipe for a nasty debate: brilliant stat spread, amazing typing (that laughs at Thunder Wave, specifically), an ability to make people miss, beautiful revenge capabilities, sheer power, and a knack for always going down with some pokemon.
What if Ononokusu doesn't even get Swords Dance or a major auxiliary move? What if he's like a metagross? Void of major stat-increasing moves? Sure, there's a good chance he'll get dragon dance, but we've got a beautiful dragon dancer already. (see Salamence) We can't be sure and throw around uber talk until we see how it's done in the metagame for some period of time.
StratusJm's got some good points, too.