Did we even get a ghost type revealed before the game hit for black and white? I can't recall that we did. Though really the only pokemon I remember them showing are the starters, Musharna, Braviary, Zoroark, Minccino, Emolga, Gothitelle and Reuniculus (if that's even right, I don't remember very well.) Maybe Deerling and Woobat (again, totally don't remember).
Though I would love for them to, Ghost is such a small/rare type that unless there are a ton of ghosts this gen or a particular ghost pokemon is really important to the plot, then I doubt we'll see one before the game is released.