As with other megadungeons, Dawn of the Infinite will be separated into two wings with Mythic+ and Heroic difficulty available in a future update to the game.
This will probably occur at around Season 3 when a new dungeon rotation’s added.
The latest Patch 10.1.5 Build 49908 adds entries of two separate wings for the Dawn of the Infinite megadungeon, which means it will be enabled for Mythic+ in the future with Heroic difficulty available:
Dawn of the Infinite: Galakrond’s Fall – The infinite dragonflight has invaded the Bronze Temple. Help Nozdormu and Chromie take back the Timeways!
Dawn of the Infinite: Murozond’s Rise – Murozond rises. Race against time with Chromie to correct the past!