Battle for Azeroth already looks close to done already, and only it's features that require beta testing like class balance and Heart of Azeroth traits are missing.
The expansion launches with more features than Legion, delusional people seem to think this means BfA is "filler" (keep in mind they said MoP, WoD, and Legion were all filler, and maybe only WoD could qualify as 'filler').
Legion Launch:
- Mythic+ (9 dungeons)
- World Quests (4 WQ zones at launch, 1 later on based on rep (Suramar))
- Order Halls
- Artifact Weapons
- Raids
- Legendaries (a bad system)
Battle for Azeroth Launch:
- Mythic+ (10 dungeons)
- World Quests (6 WQ zones at cap)
- Artifact Necklace
- Scenarios (with scaling difficulty up to Mythic level)
- PVP Scenarios
- Global World PVP server flagging and World PVP sharding.
- War Fronts
- Raids
- Removal of Legendaries (The best announcement to date)
- Allied Race quests
- Zone scaling revamp.
Let's also talk about how Battle for Azeroth takes all the best features of Legion, ditches the terrible features, and improves on it with all new content like War Fronts and Scenarios.