Disagree with most of whats been said
You don't even know if legends will bring balance because our meta would look completely different from bw or even oras. So that's just flat out wrong. Second, pokemon balance is pretty meh and tiers like bw ou have underwent some major changes due to their poor balance. Even with legendaries. If not for a very active and passionate council + community some tiers would be utter trash.
The devs should allow the council more power though, so that together with the community it has more tools to try and find balance in the tiers.