https://www.polygon.com/2018/11/3/18059740/world-of-warcraft-classic-raid-release

At a BlizzCon 2018 panel, Blizzard and game director Ion Hazzikostas revealed that World of Warcraft: Classic will not simply dump all of its content at once when it releases next year. Hazzikostas also referred to Classic as a “live game” to Polygon in an interview.

When World of Warcraft: Classic is first released next year, it’ll start with what Blizzard is calling stage one. Stage one is essentially what World of Warcraft was back in March of 2005. Players will have access to the Molten Core and Onyxia’s Lair raids. The Dire Maul three-wing dungeon and world bosses Lord Kazzak and Azuregos will be available as well.