I'm not suggesting they have to be, but I'm sick of knowing who my rival is from the get go.
What is wrong with meeting him/her around the first or second Gym? What's the big idea of giving our character and their rival a pre-existing relationship, I just feel it'd be better if we met them in-game and the relationship built up from there.
Perhaps we meet them and they help us at first, maybe they appear as a normal trainer and challenge us to a battle? Whatever, I'm just bored of the same thing.
Well, N will serve as a sort of a rival considering it has been stated he will battle us numerous times throughout the game. I think that, and our two childhood rivals have are great additions, because for me, the more long-term relationships we have with other characters the better.
In fact, I think this game may erase the whole "rival" tradition and just give us several characters we casually battle with. Personally, "rival" just feels like a spot to fill and almost excuses real personalities and roles in the story.