They try to silence just how stupid they are making the game, steering it toward casuals, and in some cases just making so everyone hates it. The ability to express your opinion is there, as long as its theres.
I doubt Bungie will make a Halo 4 specific forum, the only thing close they would make is a Halo General Discussion forum, which would include bits of everything. And MLG Doubles is far from a really relevant issue, lol. So no, unless MLG already planned to do so.