Originally Posted by
thesmall001
They've been gradually undertaking "efficient" ways to rebuild the entire old world rapidly with HD assets since WoD.
They started in WoD with Garrisons and Shadowmoon especially providing tons of general Alliance/Human, Horde/Orc, Draenei and Ogre assets. Gorgrond also provided many Botani and "Life" assets. If you look back and compare that to Frostfire, Talador and Spires, the latter all are quite sparse and lacking diversity strictly in terms of buildings, props and foliage which are the bulk of level decorations, which is the bulk of level design efforts if they were, for example, going to build Azeroth 2.0.
Tanaan and Legion obviously delivered on many Fel assets, but also brought us HD elf (and Naga) assets galore in Suramar, Azsuna and Val'sharah, and HD Tauren assets in Highmountain. Argus then provided tons of Army of the Light assets and lots of Ethereal assets, as well as a smattering of Titan stuff. The class halls and artifact quests also gave them a chance to work on all sorts of misc. assets, as well as directly update some parts of the old world like Light's Hope, Tyr's Fall and Karazhan. Oh, and Furbolgs got a whole new asset kit, and I think I recall they even updated the assets around Vordrassil in Grizzy Hills? And, of course, Helya and Odyn provided us our Shadowlands setup.
BfA was a Troll Paradise, obviously, but also gave us tons of Pirate and Naval assets in Kul Tiras which are highly reusable. Nazmir and Vol'dun also provided for "generically desert and swampy" assets, while Zuldazar provided lots of Jungle assets. Drustvar provided new gothic architecture pieces (easily reskinned) and all the Drust assets which, judging by Zovaal's magical girl transformation in 9.1, is probably the "true" Decay aesthetic. Mechagon and Motherload will provide Goblin and Gnome assets for years to come. One of the most "polished" areas of Stormsong was that entire random Quilboar area with next to no story attached to it. Lots more Titan architecture. Naz'jatar gave us the rest of the HD Naga stuff we could ever need and a top-up on all the nautical races via the Unshackled (Sea Giants, Makrura, Gilgoblins).
BfA also got them to update Arathi and Darkshore quite directly, plus the HD updates to WSG and AB. We had all the Forsaken kit updates (new plague launchers and props etc.) and the Blood Elves and Dwarves got some updates due to the heritage armour sets and their questlines. We got the Portal Rooms, Uther's Tomb got randomly updated, we got a bunch of generic assets out of Island Expeditions and Visions of N'zoth granted an entire new set of Void and Twilight assets.
Shadowlands most obviously added an entire set of almost everything Scourge related in Maldraxxus, but it less obviously added an absolute score of new animal skeletons. Ardenweald and Revendreth provided props upon props that wouldn't feel out of place in any Elf or Worgen zones. But it's the Broker and Attendant assets that really intrigue me because Arcane/Order forces are the least represented Cosmological Force in this list in terms of "palettes", and I have a strong suspicion that the "Sepulchre of Knowledge" will end up being the sealed Arcane realm of the First Ones who represent the "larger" scope of the forces of Order.
So, you take all of these, and all of the stray model and creature upgrades since WoD and you see the efforts manifest. There's not a zone I can think of in Eastern Kingdoms or Kalimdor which couldn't be rapidly re-skinned with now-existing models with only as much new asset development as would be needed in a standard expansion set. We also have sets for the 6 "warring" cosmological forces which seem to imminently need access to a battleground.
Therefore, it seems pretty evident to me, they're planning on not only doing another Cataclysm-level revamp of Azeroth but they're actually planning on setting an entire expansion in the old world without necessarily adding any new zones or continents. Instead the cosmic forces will lay claim to some zones whilst we will be granted the single-largest open world sandbox any MMO could possibly provide by scaling up the entirety of Azeroth into a free-for-all adventure to bring balance to the cosmic forces who vie to claim the "alignment" of Azeroth's nascent world soul.