I'm just hoping we finally get that dolphin Pokemon. It'll probably be adorable, it'll finally quench peoples' desire for one, and it'll stop the smart***es from bringing up Kyogre like they think they're smart. Everybody wins. I'd like for it to have some sort of interesting typing, but I think odds are best that it'll just be pure Water, and that's fine.
My NIDOKING brings all the boys to the yard: http://goo.gl/ExAoe
I'm hoping for a Water/Steel Megalodon shark. Not some half of a shark like Sharpedo, a full on JAWS.
Dolphin is next on the list, it could just be single water type, we have quite a lot of water/psychics. I just don't want to see another slew of generic fish.
I could go for another water/fighting pokemon though. Maybe a squid?
A Fire/Grass flamethrower plant thing would be sweet.
Electric/Fighting needs to happen. I always thought Electabuzz would fill this role, but apparently that is too obvious. A lot more electrics need come in any way, there is very little to choose from at the moment. It's just a crapload of Pikachus and a few good ones.
A lot more interesting flying pokemon, I don't want to see a single normal/flying one in this game, or in any future gen, ever. We have a crapload of them and the typing sucks. Mix them with electric, fire, ice. It's been ages since the legendary birds. Just don't make them suck, like Delibird.
And of course I always have to mention the Grass/Dragon comodo dragon.