https://www.gamespot.com/articles/wow-expansion-battle-for-azeroth-sets-new-sales-re/1100-6461380/

Battle for Azeroth, the seventh expansion for World of Warcraft, launched last week--and the release was a massive success. Blizzard announced today that it sold more than 3.4 million copies of the add-on worldwide on launch day, August 14, setting a new WoW expansion record. It's not immediately clear if this figure also includes pre-order sales, but whatever the case, it's a massive number. It beats the previous record of 3.3 million units sold on day one by Legion two years ago. 2010's Cataclysm also sold 3.3 million units on its first day.

Launch is just the start for Battle for Azeroth. On September 5, the expansion's first raid, Uldir, will go live. It's set in an "ancient titan facility housing horrific Old God experiments gone awry." Also that day, Blizzard will launch Battle for Azeroth's first PvP and Mythic Keystone dungeon seasons.