You know whats even sadder? There are hints that it could be the case.
1. Exodar getting ready to take the fight to Argus
2. The Army of Light being on Argus
3. We know Gul'dan is trying to make Illidans Body a new Avatar for Sageras and we will kill him.
4. Illidan is setup for a redemption story, so he will get his body back or overwhelm Sageras Spirit in his Body
Yes they could make the Tomb of Sageras a Raid, but for what? In there should be nothing of interest for us and if they could use the old avatar for Sageras they wouldn't bother with Illidan.
The delayed Island, we know nothing about it... and they have shown that they are ready to cut such things because they don't want to invest the time.
Legion should go on for 3+ tiers. Don't wanna lose my artifact that fast
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The tomb of Sargeras as of Legion is literally a doorway to Argus. Did you not know that? So they could make a SoO style raid thst starts at the tomb and ends on Argus OR how bout a throne of Thunder style patch where we have a quest hub and 5 man's on Argus with KJS palace as the raid tier.
We take the artifacts with us to Argus?
If it really is a doorway we could use (safely) why repair/power-up the exodar to go there? With the Army of light on the planet fighting the Legion is would be more logical to make it it's own expansion where we defeat the legion bit by bit and bring the entire army together to lay siege to KJ Palace.
But yes they could do what you said... but then there would be no yearly expansion
Okay how about this story line: We kill Gul'dan, get Illidans body back and travel to Argus, beat KJ come back to Azeroth to see that the Naga and N'zoth have taken over and that the titan soul is near corruption and being born. So we have the Naga/Old Gods and with them the Void Lords.
And what better time for N'zoth to strike?
I am expecting this to be the lords of war equivalent for Legion, a series of videos to be shown over the next few weeks leading up to the prepatch next month.
Last ever X-pac and they're working on World of Starcraft LOL
Vanilla server access! ... if you buy legions