Analysis of the Dragonflight Announce Cinematic Trailer

wowhead.com:

The cinematic begins with a close-up of the lit Beacon of Tyrhold, a titan-forged tower built by Keeper Tyr on the Dragon Isles. We are told the scene is from 10,000 years ago, and as the camera changes focus to zoom out, we catch our first glimpse of an area that we now know is Thaldraszus, the seat of power of the Dragon Aspects. In the distance, we see a storm, green light at it's center — the Sundering. The Great Sundering was a cataclysmic event that marked the end of the War of the Ancients — caused by the destruction of the Well of Eternity — which tore the world of Azeroth apart. At the time, the Dragon Aspects were the guardians of Azeroth, empowered by the Titans and tasked with the duty of protecting this world in which a slumbering Titan lies. The scene changes to atop the tower, where we see a Watcher — a titan-forged stone being created for the duty of watching over certain areas. The shadows of dragons fly overhead — the dragonflights, needed by Azeroth, are leaving.

The Watcher takes a moment to look over his shoulder at the Sundering — another Watcher seems almost captivated by the sight — before he turns back to his duty, turning a device at the base of the Beacon, shutting it down. As the Beacon deactivates, clouds begin to roll in and the skies darken. We catch a glimpse of a Watcher in the Waking Shores as a shadow falls across the land, another Watcher on the shore of the Dragon Isles as the clouds close ahead, finally blocking out the sun completely.

We see Watchers of the Azure Span, going dormant along with the land as Alexstrasza