From Blizzard’s blog and Press Kit, we know that we’ll face down both Iridikron and Galakond in the Dawn of the Infinite Mega-Dungeon coming in Patch 10.1.5. A few press kit images show both the skull of Galakrond and Iridikron together as well as a normal sized model to indicate the sheer size and scope of this dungeon.
You’ll face Iridikron and Galakrond, among others, as you work to sustain Azeroth’s timeline and put things to rights once more.