Name is Shadow over Azeroth. It has to do with one of the void lords casting sort of a void barrier thing over Azeroth. Illidan comes back to warn us just before and Sargeras is out of his prison. He's not redeemed from what I gathered but is working alongside the other titans now that they've realized the threat of the void. He pulls out the sword out of Silithus and through the hole we travel to Uldaz. There is a teleporter pad there which takes us to Khaz'Algar, which is underground, like way waaay underground. The earthen have become "corrupted" by being too close to the titan soul of Azeroth.
Heart of Azeroth is back and Khaz'Algar can only be entered if you have the neck equiped. Major world revamp with lots of void portals opening all over similar to Legion Invasions.
Fun Fact: The trailer is narrated by knaifu.
World revamp is happening, many zones will count as end game zones in one way or another.
The earthen of Khaz Algar act as protectors to the world soul and have been at war with minions of the void /old gods that seep through as their "roots" get closer and closer to the sleeping world soul
All races get shaman, no new race at start, shaman tank spec, demon hunters get a ranged spec
2 new zones, both underground, a lot of leveling and endgame outworld content happens on azeroth, dragonriding on azeroth, dragonriding renamed to advanced flight, all flying mounts get it
8 new dungeons, 2 underground, 1 in northrend, 1 in pandaria, 2 in kalimdor, 2 in eastern kingdoms. 1 new raid.
Twilight's Hammer and its cultists are back and led by Xal'atath.
Updates to archeology and more focus on inscription.