I know I'm starting with Mudkip, but besides that I don't really know.
My original Ruby team was Swampert, Pelipper, Medicham, Banette, Mawile, and a Shelgon I could never get to evolve.
Besides my starter I'm going to want to change it up a bit--I love Mawile but I've created a competitive team around one in X so I'd kind of like to use something new.
I was also thinking of catching another Meditite/Medicham to use as a Mega for Omega Ruby, but if Swampert happens to get one I might just forgo Medicham altogether this time around.
If they include newer Pokémon in these games, I might use a few of them, but my focus will be on Hoenn Pokémon.