The tearing off of the robes and the casting away of the staff suggest to me that he's basically quitting his job as head prophet, or whatever. Like 'take this crap seriously or I walk' type of thing.
Anyway, bummer on Zandalar sinking, because I really wanted to see the place.
Although... if there's a naga related expansion and Azshara starts raising crap from the ocean floor, that makes Zandalar a candidate. Giant un-sunk troll island full of ruins and ghosts and such...aw yeeaah...