I'm actually one of the very few hoping that N is Gray. When I think about it, that would be pretty cool.
It actually would make sense. Even though the manga is portraying him as more antagonistic than anything right now, it'd be just like Pokemon Special to throw a curveball like that at us.
Other than that, I think "Grey" would be an original character, considering the pattern so far, they seem to be creating an OC for every odd number gen. Or maybe something weird will happen where Bianca and Cheren share a dex and combine to become the third 5th gen. dex holder. Just trying to think outside the box...xD