I would be really happy if both Iridrikon and Vyranoth manage to stay alive but have their power lessen than only one remaining alive and its alignment changed. Their ideals matter in this conflict and they shouldn't be changed. They are interesting character and this expansion should carry on most of its interesting cast (let it be visually, story based or character based).
One way they could also accomplish this is the same way they've ended wc3 they need to face off a common evil (let's say dark Tyr) and realize that what corruption they see in their foe is kind of a necessary strength because alone they couldn't have win against their common foe. Then they go their way promising to remain ever watchful of the aspect and to bring them down if they ever stand against them when they will rid the planet of the evil titan watchers Odyn or some other shenanigans.