I'm still guessing its a human. Zekrom is like white on rice(Reshiram), you can't show one without the other, unless Reshiram is appearing too, then there's Kyurem. I guess its Meoletta if it is a Pokemon.
You've said this a number of times, but think about it--when has a movie title ever referred to a human character? Hell, when has a movie ever focused on a human?
Besides, the Musketeer Trio's card decks are being released next spring and Keldeo's the next phantom Legendary to be released via an Event. It's fairly obvious it's Keldeo.