I don't really like electric types so I hope that Zekrom turns out to be part Dragon and part Dark. It would still be a unique combination.
But even that doesn't really matter to me that much. I just hope that Game Freak gives the Legendaries an ability other than Pressure. I'm so sick of that ability, I wish they'd give it something unique.
I wouldn't mind it being Dragon/Electric or Dragon/Dark, simply because their unique, and it would be interesting to see what movesets it could have under it's belt.
And I agree with you on the abilities, Groundon and Kyogre has Drought and Drizzle respectively, which brought Rain or Sunshine into battle as a whether condition on the first turn without using sunny day or rain dance. Then Rayquaza has Air lock, which stopped the effects of the weather, and on Kyogre and Groundon's abilites, referring back to Hoenn mythology, with the battle between Kyogre and Groundon which was ceased by Rayquaza.
It's practically obvious these two new legendary Pokémon are going to contrast, Black and White are clear opposites. And with the amount of references to the Sky, (Hiun means clouds floating in the wind, the bridge leading out of Hiun can be translated to Sky Arrow Bridge)
Water Pokemon Master @ Pokebeach said:
As we posted yesterday, Reshiram's name comes from "shiro," which means "white" in Japanese, whereas Zekrom's comes from "kuro," which means "black." But as it turns out, the names also originate from the Japanese words "shiramu" and "kuromu," which mean "to grow light" and "to grow dark."
I can see their abilities being related to Night and Day, based on all this evidence. Although they're currently not weather effects or effects in battle, the only effect on the battle is that they change the backdrop depending on the time. Maybe in Gen V, Night and Day have hidden effects?