Well, IMO, Reshiram looks to be Dragon-Light, and Zekrom looks to be Dragon-Dark. Now before we start bashing that there won't be any moves for the Light Type (if there is one), anyone remember Bite from Gen 1? They changed that from Normal to Dark in Gen 2 when they did the mechanics of the game, so it wouldn't surprise me in the least if they did it here as well.
I will be pissed if Reshiram is Dragon-Flying. I mean, they already have a few of those. But I think these guys should've been something else other than Dragon to begin with - weren't there enough Dragons in previous generations? Especially with Dialga, Palkia and Giratina from Gen 4? oO