They're adding clauses so in that aspect, it's Ou. Other than that, it's not, as the banned legendaries are not limited to ubers, no megas are allowed, and there are 2 available ubers for challengers to use. I should think if you so desired, you could make an ou team, providing it doesn't include any legendaries or megas (or swaggerers, etc.) but to do so would prevent you from being able to use greninja and aegislash against teams that will eventually have the potential to use uber megas. So the only benefit in doing so is that you can practise with it more easily on the main showdown server. Once again, if I'm wrong about any me this, by all means, correct me.