Bronzes have their own class - Timewalkers, so they wouldnt be a part of "Dragonsworn" and pretty sure no one would wanna use Blue powers since Malygos went insane.
Black - Tank
Red - Spellcaster
Green - Healer
sounds more likely if Dragonsworn was to ever become a class.
If they make another class, its gonna use mail, or it should anyway, another clothie will, rightfully so, throw the lock/priest/mage people into a shitfit.
^ This. And now to mention things that will get me yelled at by lore enthusiasts:
The thing about a dragon-based class would be that one color could effectively serve for any or, more than likely to be the case, all roles. Although Wrathion might stick to his own dragonflight, it's possible that the story could involve finding his father's research on other dragonflights and applying it to the creation of this new dragon class with a means of transferring such power onto mortals or something along those lines.
I also wouldn't expect transformations, at least not complete combat transformations when that style is already owned by the druid class. If for some reason there would be transformations, they would probably be within particular attacks rather than a permanent form (best example being a couple of attacks from the assassin class in Aion). However, they still need some sort of a set of auras or aspects to mark a definition in a group role, so there could be a possibility of dragon-like body parts like claws or horns or a tail. If there is something along the lines of metamorphosis, hopefully it won't look like any other sort of dragon-like model currently in the game.
Last thing is on the roles. If it's going to tank, it will require a whole new mechanic for mastery that wouldn't involve armor (druid), absorption (dk), blocking (warrior & pally), or whatever stagger would be considered; leaving a possibility that this class may not have a tank option. If it's going to heal, it may likely be the winner for indirect healing, likely working along the lines of how the green dragon in the oculus performs healing. DPS would offer greater options, but will probably wind up being a caster given that the past two class additions were both almost entirely melee.
TL;DR - game mechanics before game lore, possibility before desire.