Shoot! You beat me to it!
I JUST saw the trailer and was going to post this too!
Well my thoughts are:
Chespin: What an odd grass type Pokemon... It's a parody of a chinkapin chestnut. It's almost like Seedot as a starter. The moves it used look like Solarbeam and Night Slash. Two assumptions from this Pokemon:
1) It's starting attack move might be Scratch
2) It's secondary/final form might be a Grass/Dark type. If so, it would ironically share it with Nuzleaf and Shiftry species, who evolve from Seedot.
Fennekin: A fox Pokemon. Ironically, not the first fire fox we had (Vulpix and Ninetales take that honor). This Pokemon looks like it can learn Flamethrower and Psychic. This one is based off of a Fennec Fox, a scavenger hunter in the Northern Regions of Africa. Three assumptions of this Pokemon:
1) The furries, anime-junkies, and girls will all choose this Pokemon hands down. They won't even bother looking at the other two.
2) It's starting attack move must be Tackle
3) It's secondary/final form might be a Fire/Psychic type. PLEASE let it be this! I seriously do not want another Fire/Fighting type starter for the fourth time in a row! (Blaziken, Infernape, Emboar).
Froakie: There are already a lot of frog-related Pokemon (Poliwag, Poliwhirl, Poliwrath, Politoed, Tympole, Palpitoad, Seismitoad, and I might have missed a few). It looks like it either knows Water Gun or Hydro Pump and it looks like Close Combat. Two things about this Pokemon:
1) It's starting attack move must be Tackle
2) It's secondary/final form might be a Water/Fighting type. Not a first in the water type Pokemon, but at least it's not a Fire/Fighting!