They're going to troll and reveal Fletchling's middle evolution, just because out of the other Pokemon revealed so far, it just screams that Fletchling would be revealed before the starter's just because of the odd skip in stripes for Talonflame.
Plus they seemed to have revealed Evolutions in packs, like Scatterbug's evolutions wasn't revealed on their own, same goes for the Starters. only exceptions was Pokemon that was initially revealed to have evolutions later such as Pancham, Litleo and Gogoat..latter of which was inversed with Skiddo.
Since they said "a pokemon" it couldn't be Clauncher or Skrelp, due to their nature as exclusives, same goes for Swirlix and Spritzee, they never revealed an evolution for an old Pokemon so far, they may have been trying to avoid hints that would suggest that they're catchable in Kalos.....barring the occasional close up slips like Marill (on beret girl art) and Zigzagoon. (very closely on the Pokedex art)
EDIT: forgot Sylveon, but that seems like they're trying to reveal Fairy, would it be slightly redundant to reveal something like Dragon or Steel eeveelution?
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