This item is reported: two Blizzard designers in an interview on a creator's channel, not an announcement. The quotes come from the video's automatic subtitles, which name no speaker, so we attribute them to the interview.
The black market
Powderfuse Port has a black market auction house. The reason is the gold supply: players "are essentially walking printing presses", and the game needs "places for the gold to go". At launch it sells a few mounts and pets, dungeon drops such as Gandling's hat, and dungeon set pieces needed for the Lord Valthalak quest, which grants a Legacy point and spec-specific gear. A second vendor sells rare resources, Black Lotus among them, for gold - as a "price ceiling". Rivendare's Deathcharger was taken out of the selection during the beta: "Never say never."
Raids and hidden loot
The raids open on 9 December as "a global launch". Addons are restricted to keep an arms race between addons and encounters from starting. The target difficulty is "the typical Naxxramas encounter. Not the hard ones": harder than Molten Core, not as hard as the Four Horsemen, and longer than the 45-second kills of 2019. Barrow Deeps is compared to Karazhan and should be pug-friendly after a few weeks. Loot is flagged to stay out of the client database until someone loots it, and that will continue for future raids - "I love this concept of the unsolved game." The live clients of 7 November already show items appearing this way. Every boss also has a small chance at "chase items", some of them at a higher item level.
The world
There will be no flying: "very clearly, we're not going to put flying mounts in this game. Not going to happen... That's kind of a never." The map was built "as if you could fly", without empty voids, because of the longer view distance. Gilneas is the Cataclysm version for now, with a no man's land around it on purpose. New boats run to Southshore and from Powderfuse Port to Tanaris. On lore: the Riverglades draw heavily on the Second War, and the Skyborne have "much deeper history" around southern Desolace and Dire Maul - "When you go to Shen'dralas, pay attention to who you're talking to."
Test realms
A PTR for general stability is "very likely", but they "somewhat doubt" raids will ever go on one.
What this changes here
The Shen'dralas page gets nothing new from this - "pay attention" is a hint, not a fact. The build chronicle notes the hidden loot under the client of 7 November.