They're not giving us the Argus raid when 7.3 launches, they'll do just like they did with 7.2 which worked out perfectly. So the patch is probably out late July if we're optimistic or mid August and by then we'll have more info on the last boss of the raid as well. So I think we can see a new expansion reveal during Gamescom. Maybe even pre-patch info.
If not there then we'll definitely see it at Blizzcon.
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They said in an interview after last blizzcon I believe, that they're doing some new stuff with hair and customization, I think they were aiming for 7.3 but it probably got postponed into a 8.0 thing. They wouldn't make that kind of stuff for a normal npc that share the same skeleton / model as a player model.
I cannot remember who it was that held the interview but it was one of those one to one interviews with the devs after the presentation.
I believe it was Chris Robinson and one more dev there.