Considering how many times Blizzard has retconned (justifiably) TBC's cracked out experimental lore, K'aresh probably still exists in some form and will be an Argus-type exploration area in Midnight.
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I think there is something to be said about how Chaos and Void seem to be very similar in MO. Similar to how Light and Order seem to be aligned to the point that they use each others powers. Why are the two pairs so buddy buddy?
Yes, Sargeras hated the Void and started the Crusade to stop them, but demons use shadow magic all the time and both parties are all about ultimate freedom (from titans) at any cost. The only reason the Crusade was as structured as it was because it was ironically created by a Titan.