Okay, I've done much research on these two, so I'll reveal what I know.
As far as getting them in America, it may be possible. If the movie enters America in theatres (Sorry, Canadian spelling of the word :P), then chances are Toy R' Us will do a promotional handout event for getting Zorua and Roroark at some point. This is just speculation, but it's bound to happen at some point.
As for Zorua's and Zoroark's ability, Illusion, it's influenced by who's in the second slot of your party when either one of them is switched out. So if you had a Lombre in the second slot of your party, then Zorua/Zoroark would adapt the appearance of that Lombre. However, stats, nature, type, moves, and others will stay the same.
This ability will be useful for tricking a pokemon into, say, using a Psychic attack on the illusioned Zoroark or Zorua. Or shifting into a Bird Pokemon to keep the opponent from using Earthquake.
