Well, Kyurem's 2 forms are the mascots of the game. I guess I neglected to post the box art.
So I think "the story will do something with Kyurem" is pretty much a given.
As for the other stuff, I'm fairly sure it's typing will stay Ice/Dragon. All three of its signature moves (Glaciate, Ice Burn, and Freeze Shock) are Ice-type, so there's no way that's going, and I doubt they're going to cripple it by making the forms Ice/Fire and Ice/Electric. In stats, it may be as simple as Black Kyurem getting +20 Attack, and White Kyurem gaining +20 Sp.Attack. Kyurem is 20 base stat total weaker than Reshiram and Zekrom are, and bumping either offensive stat by 20 would line it up with the higher offensive stat of the respective dragon, making it so Black Kyurem would hit just as hard physically as Zekrom does, and White Kyurem would hit as hard specially as Reshiram does. As for the ability, right now people are guessing the forms will have a new ability that negates the charge turn of two-turn moves. Both Ice Burn and Freeze Shock require a turn to charge (like Solar Beam or Razor Wind). This would make it so normal Kyurem would have to charge these moves, but White Kyurem could use Ice Burn with no charge and Black Kyurem could use Freeze Shock with no charge.
All of that is speculation, of course, and I'll post any concrete information when it is available.