So the system is balanced. Okay, and? Most people know this and most of the people arguing for a new type aren't doing so for the sake of what they perceive to be an unbalanced system. Usually, when someone suggests there should/will be a new type, it is because a) they want a new type and think it would be cool, or b) they see a Pokemon like Reshiram.
And although the fact that the Dark- and Steel-types were necessary additions to balance the game, making the introduction of a new type appearing improbable, it doesn't make it impossible.
This is Pokeyman we're a talking about, a video game. Anything is possible and the creators will do anything to keep their audiences money in their pocket happy.
Also, I've seen nothing wrong with Ravecat's speech. In the post that sparked the mini-conflict was a bit of mild sarcasm, but it was directed at you, HannahMontana.