Hydaelyn doesn't have to be a bad guy for us to go WoD. One way or another there was a conflict between Hydaelyn and Zodiark that resulted in the world being split. The thing is, even if she wants to, Hydaelyn cant fix that because she is only a being of light. She, by definition of her nature, cant bring balance. What is needed is a team dark that is open to a final balance and everything we have heard about team Ascian is they want Zodiark to win. The thing is, Zodiark, by his very nature, cant bring balance either.
I think we will be going WoD, not because Hydaelyn is the enemy, but because someone has to take over the role the Ascian's play in maintaining balance. That is in reality the only way we can stop the Ascians permenantly without it triggering a Flood of Light. I do think in Shadowbringers we might get a better learning about why the Darkness is necessary but what is needed is a non antagonistic agent of Darkness who is willing to look on how things could be fixed rather than just carrying on the same conflict that has lead to this situation and caused so many Calamities.
Our characters and the Scions need to find a third option, something that has been the case since we learned Albert's story. I actually have a suspicion that that has been Hydaelyn's intent from the start. Consider the theme song Answers. In it Hydaelyn is basically saying you have to understand and go through the pain of living to understand life's worth and grow. Her words at the very start were her telling us to learn for ourselves.
When we come into the story Hydaelyn is pretty much about to lose. She has lost every encounter so far and she is so weak that in HW she cant even communicate with her champion anymore and needs Minfilia to be her mouth peace. This state is confirmed by the Ascian's dialog stating that she is weak. People think she doesn't care because of what happened to the first shard but if she couldn't even communicate with her own champion on the source it isn't a stretch that she would be completely powerless to stop what was happening on the first. It is only due to being bolstered by the Crystals of Light that she is able to free her emissary to do anything about it.
Currently we are team Light and the Ascians are team Dark. That is a fight no one wins. In the end we need a team Light and a team Dark that can find a middle ground and that almost certainly requires replacing team Dark.
I also feel I should state that Solus himself said he only created the Garlean Empire to create a source of chaos and strife and frankly they have lived up to it. Much of the disasters and even the spread of Primal summoning has been triggered by their aggressive and expansionist approach. That doesn't mean that the Garleans are inherently bad or that most of the empire don't want to achieve order, but that effectively and quite ironically the Ascians have been using achieving that goal as a justification for causing the exact opposite.