I just got back from pre-ordering Pokemon Black. I've not checked anything on the games, but the guy who works there kept saying you NEED both to finish.
Also, I used Action Replay to get the 3 GameStop Exclusive Shiny Legendaries for HeartGold since I only found out about them yesterday... Not fair, so I made it. It says those Shinies unlock Zoroark in the new games, right?
Anyway... I also had tacos.