A personal theory of mine is that Zodiark as of now is no longer our enemy, but due to his containment hasn't been able to stop the Ascians from doing what they do, which isn't helped by some of them also working towards goals that weren't exactly conductive to serving him even back before he was contained (IE things like Lahabrea all but saying he was gunning for personal power while talking to Elidibus). Regardless of who the voice speaking to us/the Scions is I think Zodiark has something to do with it, and his containment could very well be affecting it which caused the whole soul taking thing...possibly.
Some other posters have also talked about how it seems like Amano's artwork positions the WoD protecting the light...so ya know, we Assassin's Creed now. Working in the shadows to protect the light and all that.
Ishgard rebuilding is probably something that starts happening in the 60s honestly, and even if it doesn't probably won't be affected as much by the Shadowbringer story. At most however the xpac ends will lead to Ishgard being able to free up resources to speed up infrastructure recovery. As for Trust, it depends on what NPCs will be available, which we don't currently know.
AS FOR the enemies that both the WoL/D and Thancred face in the trailer, a reminder that while Amdapor was not as aggressive as Mhach was in their war, White Magic did quite a bit of devastation as well. The elementals of Gridania were also kinda freaking out about the Amdapori constructs coming back online as well (thus the HM City fight). So "Light" has already been shown to be dangerous even if "Dark" has been a more constant threat.