Blizzard
In Battle for Azeroth Season 4, the maximum stats on rewards from Mythic Keystone dungeons will be increasing, with item level continuing to improve up through Mythic 15. Completing a Mythic 15 dungeon in Season 4 will award item level 475 gear in the weekly chest (this is equal to Mythic raid quality), and the maximum end-of-run reward will be iLvl 465.
With this change, we seek to better calibrate rewards to the difficulty of high-end Mythic Keystone dungeons, as well as to ensure that in the absence of the random chance for Warforged/Titanforged gear in Season 4, players still have an opportunity to earn rewards from the Mythic Keystone Dungeon system that are equivalent to high-end raiding and PvP loot.