Don't listen to JustRob. No one who has read his past posts and comments take him seriously.
Former highend raider. Now highend moron
Let me get this straight. There is evidence that Yogg and Cthun are dead, just like YShaarj, yet Cyrisela refuses to believe it even though no evidence points to the contrary? Makes sense.
AFAIK Old Gods die, but their corpse still contains power which continues influencing the land, mutating those that consume it, and in general having a radioactive-like influence. They are not demons - they do not return to the twisting nether waiting to respawn.
If Yogg is dead, who accosted us in Ulduar during the Legion launch questline?
I think the Old Gods are dead (except N'Zoth) as in their physical manifestations are dead. Since they are a physical manifestation of the Void it might work a simular way as demons with the Twisting Nether? And that the ressurection part on Old Gods is simular to summoning/ressurecting the demons from the Twisting Nether.
On top of that, the Void is considered a greater threat than Sargeras and his Burning Legion. So I doubt they are truly killed off this easily. Or they might just be lowly pawns compared to the Void Lords.
Perhaps on Mythic the item Shadow Priests can use to have their weapons speak to them after Xavius is dead will instead open a portal to a new boss room!
I can dream, right?