TLDR
Main enemy is Chromatus, though lots of minor stories all about.
6 disconnected zones (2 of them being revamps).
4 new micro classes (1 spec each) instead of one full new class.
Class ‘skins’ for some preexisting classes.
Player housing.
Carpenter and Logger professions.
Dalaran capitol city.
No level cap increase.
Rewards from Shadowlands just get scaled down. Everything in 10.0 is max level content (level 60) with no level squish, so there is no need to level if you already have max level characters. Progression is just endgame progression.
Dragon Isles. Technically its own continent though it’s just one zone split into multiple maps. Floating islands between the Broken Isles and Northrend.
Lordaeron. Revamped Tirisfal/Plaguelands. Scarlet/Light focus.
Quel’thalas. Revamped Eversong/Ghostlands. Silvermoon is a hostile city like Suramar.
Undermine. City-zone beneath Kezan. Criminals and Uncrowned story. Fully underground.
Balor. Halfling race dealing with primordial fel enemies (think proto-demons, like what the Shadowlands creatures are to undead).
Uldaz. Second fully underground zone ever on Azeroth. Titan/Elune story here.
Dragon Knight. Only one tank spec. Uses two-handed weapons, fire, plate armor and shouts.
Tinker class. Only one damage-dealer spec. Uses guns, mail armor, gadgets and mech suits.
Minstrel class. Only one healer spec. Uses leather, lutes, violins and panflutes.
Chronomancer class. Only one healer spec. Uses cloth, time magic, and sand magic.
Dark Ranger skin for Hunters. Dark spell effects. Tames undead instead of animals.
Necromancer skin for Warlocks. Plagues instead of curses. Summons undead instead of demons.
Nightmare skin for Druids. Corrupted spell effects and animal forms. Can unlock wildly different forms (that play the same as normal druids) like snakes and spiders.
Dragonsworn skin for Shamans. Draconic spell effects and forms.
Warden skin for Demon Hunters. Uses arcane and holy magic instead of fel.
Continued Order Hall stories, though only a select few and you pick them like Covenants. There are no gameplay differences between them, just different campaigns, mounts, mogs and companions. The Silver Hand, Uncrowned, Kirin Tor, Valarjar, and Black Harvest. You are not considered the leader of the order.
Expansion announcement February 28th. Announcement for the announcement planned for the 18th. Goal is to release Q1 2023.