actually he is being mentioned in 5.2 lore.
he is king of the zandalari the very same that we fought in 5.2
however before the sundering happend 1 of his prophets had visions of their isles destruction, the king and other advisors didnt heed too his calls, but he gave that prophet the resources he needed too flee on a fleet with zandalari trolls that believed said prophet.
and it are these zandalari trolls who have been causing so much trouble on the rule of the dark prophet believing their isles have been destroyed and in his guidance believe they should rebuild their ancient empire.
however we dont know what truly happend too the king and the trolls who stayed, its easy too assume the cataclysm hit them too some effect. but wiping them out? that is something i myself dont believe.
they will however be not as strong anymore as they were since a part of their population already left and they must have suffered losses from the cataclysm when it struck. im looking forward when they will be introduced agian.