If they evolve Gyarados, might as well evolve Milotic. But I get what you mean, though.
Y'know, I've always wanted to see an evolution for Dunsparce, Pinsir, Mawile, and maybe Torkoal; and it's about time that Kangaskhan's baby came out of that pouch--what was the fan name for it, Kingoskhan? Also, one thing is for sure; we'll see more baby PKMN.
But yeah, like you said, maybe of the 100+ possible new PKMN, probably half or less will end up being actually new ones. We'll see when it comes out...
EDIT: It just occurred to me: what if they make an additional evolution for female Machokes? Or end up making the Machop line all males and introduce a new female Machop line? Might as well make Gardevoirs female, too. Just a random thought I couldn't let go...ignore if you want.