I'm going to go out on a crackpot idea.... The Dark (Black) Hero is Genosect.
Why? Well here's my reasoning:
- Victini and Genosect are on opposite ends of the Unova Pokédex, making them opposites and thier types or moderately opposite (although Victini still holds the advantage, but Genosect w/ a Aqua Cassette could make the battle interesting).
- Genosect suffers from a similar dark past to that of Mewtwo. He's is a pokémon that has been experimented on. He's not truly evil, but he may harbor some ill-will toward humans due to what Team Plasma has done. In the end it would be up to Victini to quell his rage.
- This would make the movie similar to the first movie, which if you haven't seen the BW anime it's very similar to early Pokémon episodes... Ash travels with two Gym Leaders, Team Rocket is actually threatening, Ash knows next to nothing about catching/battling, etc.
Anyway, yea... I think Genosect (who has yet to receive official art.. the pic above was drawn by Xous54 as was the Kerudio image). What do you think?
*Update: A new trailer shows both Victini and Zekrom, however it's unclear if Zekrom has a major role in the movie or if it is the Dark Hero. The trailer shows Zekrom basically raging using electric attacks and Victini launching a fire attack, but in different scenes (Zekrom in a mountain setting and Victini over water). Since they aren't interacting with each other it's hard to tell. Also it's common for scenes in early trailers to be solely promotional and never actually appearing in the movie. For example, an early Trailer for Giratina and the Sky Warrior had Regigigas bursting out of the ground in the middle of a Gracidea flower field but in the movie it awoke in a snowy temple and never actually interacted with the flower field.
**Update (1/14/10): Yep.. Zekrom is totally the Dark Hero now. Meh. I was hoping for something not quite as obvious...