This is what I wanted it to be.
The corpse that is featured in the trailer is the reincarnation of the "Ganondorf"/Demise intended for the Breath of The Wild timeline. (The one I'm using to support this notion is the curse that Demise put in for the descendants of Link and Zelda)
That entity never wanted violence at all. And because of this, the curse that Demise has put in is actually having some conflicts with the ideology of that entity. As a result, the pure malice and hatred became Calamity Ganon. I also think that this is not the first time it happened since there was a tale 10,000 ago where Calamity Ganon also appeared.
What happened during the era of BOTW, is that maybe this entity knew about the possible catastrophe this might entail, so he seeked the Royal Family for help. They agreed to seal him in the basement of the Hyrule Castle just so they can monitor it closely.
During this time, I think is where this whole Yiga Clan thing was also formed because of the technological advancements the Sheikahs are actually getting. And somewhere along the way, they want to teach them a lesson. Now that's when they remembered about that sealed entity in the basement of the Castle.
The Idea they have is that, if the Calamity Ganon were to awaken and takeover the tech that the Sheikahs developed, they might stop continuing further with this. It may also result to the extinction of the clan, which will render the tech more of a relic of the past.
That may also be the reason why Ganon had some Sheikah tech in his boss fights. Maybe the Yigas took the blueprints to help aid Calamity Ganon with this plan.
As for the green energy on the trailer, that's where I come empty handed. I don't have amything where I could tie that up.
Anyways, that's my scenario on what I think it should be. And if this were to happen, BOTW 2's placement will be at the very end of the timeline as it will be the part where the cycle of Demise's curse ends, and all Zelda Games moving forward will be placed before BOTW.