Considering we've already seen one dragon (Slane), plus the void dragon from the last game, and there was another dragon in the early showcase of the game, yes, there will be presumably several dragons No reason you won't be able to play as them.
I suppose it's an interesting possibility given the history of playing a dragon in Divinity 2, and Slane is another dragon knight...
No reason you won't be able to play as them. 
