I wouldn't really guess their themes based off their first stage either. For example, no one really guessed that Fennekin would be based off of a mage till Braixen was revealed. I'm also getting flashbacks to the whole "wottergate" situation. For those of you who weren't around for that, in Gen 5, a concept sheet of the starters and their evos were leaked, and a lot of people assumed it was fake because Dewott became quadruped when it evolved (at the time we also knew about Servine and Oshawott because of an anime reference sheet leak).
Turned out, Pignite was revealed in a corocoro, and to the shock of most people, Samurott was real!
Now I'm not saying that these concept images are real, its just that I don't see anything in their design that suggests that they're fake either. If they're fake, I imagine we'll find out in a different way, such as say, getting a gym leader reveal.