Don't really ever see NZoth making an appearance, unless we somehow find a way to summon him or get subs that will dive deep enough and comb the ocean floor for an entrance to his kingdom.
He is the weakest of the old gods, preferring to manipulate from the shadows. In a way, he could even be helping us keep the stronger ones at bay and imprisoned thru his manipulation, keeping his presence the strongest.
After all, what fun is a conquered world when your designated beneath your brethren with no one to manipulate and control? Sure, his followers pop up from time to time, but don't forget that thru his schemes and machinations he has the potential to be controlling more of Azeroth than is known.
That's terrible. Full blown old god expansions defeat the entire point of old gods. Old Gods are subtle like what they are based on (lovecraft). That's why cataclysm story sucked. Twilight's Hammer went from cool cultist organization who did secretive stuff to a brute force army. Deathwing went from master manipulator to raw force.
The MoP approach was the best. A slow reveal over the course of the expansion that there was a remnant of an old god right in the center of the continent. We already have this for Battle for Azeroth. Bot continents have old god influences (Gh'uun/Sea priests/naga).
BfA is clearly a first expansion in Void Lords saga in the same way WoD was ultimately a setup for Legion.
I think it's pretty obvious that by the end of BfA we will be tangling with Old Gods and Void Lords, Azshara was already teased as a raid encounter and what is she if not the agent of Old Gods and thus Void Lords by proxy.
I am pretty sure after Azshara, Nzoth is next and he will be the link between BfA to whatever comes next.
N'Zoth is the strongest Old God.
Yes, he used to be the weakest. But the Old Gods are tumors; their power depends on their size and the power they hold. N'Zoth was the loser there, as he lost important sites like the one where the Tomb of Sargeras now stands, to his competitors. But as the Shadow Priest dagger states, in the end it was always going to be 1 Old God left that gets to consume Azeroth.
The Old Gods are competitors. They limit each other's growth. As long as more than 1 remains, they cannot reach their full potential. N'Zoth is now without competition (outside perhaps the creature we encounter in BfA's first raid).
C'thun's tendrils were limited to the area enclosed by the Scarab Wall for 1000 years. His growth was small, and his power dampened. It is by far the weakest Old God we have faced.
Yogg-Saron was more powerful. Though the Great Trees limited his spread to the northern parts of Northrend, he had broken some of the seals on him, and regained more of his former power and territory than C'thun did.
But now C'thun and Yogg-Saron are dead. And sure, Old Gods do not slumber restfully. Their corruption will haunt the land till the last shred of their power is spent, like Y'shaarj was. And they are not beyond resurrection. But currently, the only Old God that is active and able to grow, is N'Zoth. He has already shown his influence in territory that belonged to Yogg-Saron in the past. We see his influence as far as Blackfathom. And apparently he is struggling against the last of his seals. Soon we will have an Old God that is free, and able to grow out into his mature form. We have seen what that looks like:
So why is he not hyped as the final boss?
Because he wouldn't sell the expansion. Some of us love the Old God lore. Not all of us. For the casual player, the lore heroes of Azeroth are much more appealing. The Horde and Alliance are. Not N'Zoth, nor Azshara, would bring in the amount of players that the current approach will. The story of N'Zoth will be brought to us in the setting of the faction war. The same way the story of Garrosh uniting the world against him, was told in the setting of Pandaria. The theme of the expansion is the decoration. It tells you little of the story. We will definitely see N'Zoth.
Queen Azshara is a suitable final boss for sure, but I could say the same about every Legion tier really
Were getting some old god tie-in with the blood troll raid btw. Don't want to spoil anything.
He most likely will show up as the end boss of BfA, and then Void theme after BfA... since Old Gods are part of that.