While that is possible, there is absolutely no freaking way he will be the last boss of the Argus Raid instance. That isn't happening, so the only other question is, how will he fit into the gameplay that suits the story IF (and thats a big doubtful IF) he survives? Never forget that they will put gameplay in an mmo before the narrative.
For the Horde!
Mac'Aree should literally be a Twisted version of the Exodar (That's pretty much how it's described in the Illidan book). Everything else on the plenet should be a pile of ash, I mean come on, this is the Legion HQ, not Elunes vacation home.
I wonder who will we even fight on Argus as raid bosses. Blizzard sliced too fast through too many important demons. Who's even left if we assume they won't repeat raid bosses (and dungeon also) we already fought?
Oh sorry...I meant there.
Would you like that if Argus had a intro like Tanaan Jungle, but with demons instead of orcs, and other related stuff?
Kinda like we invade the demon's world, but we get overwhelmed so we have to flee to a Army of the Light stronghold...
We also meet up with familiar faces too, and would be nice if we got our own themed named npcs helping us with the invasion.
Let's say you go do the Argus Invasion with a Monk you get a small group of named npc Monks that will help you, and the same with the other classes.
For the Horde!
Personally want Kil'jeadan to not die in the nether so we can have a Bro's unite fight with Us and velen vs both Kil and Archimonde at once
For the Alliance, and for Azeroth!
I really the art team make Argus like the hell itself, with reavers of souls of the people who defied the legion, forges of soul with a creepy and nasty appearance and the earth itself seen very evil and dirty.
I hope Yrel will join us for Argus c:
Kil'jaeden: BROTHER! Is it...over?
Velen: At long last. No lord rules forever, my friend.
Kil'jaeden: I see...only darkness...before me.
Velen: Without its master's command, the restless Legion will become an even greater threat to this world. Control must be maintained. There must always be...a Demon Lord.
Khadgar: The weight of such a burden...it must be mine, for there is no other to...
Illidan: KHADGAR! You hold a grim destiny in your hands, brother, but it is not your own!
Khadar: Illidan! By all that is arcane...!
Illidan: The demon's flame...sealed my fate. The world of the holy...can no longer comfort me. Place the necklace upon my neck, Khadgar. Forever more, I will be the jailer of the demonic!
Kadghar: No, old friend. I cannot...
Illidan: Do it, Khadgar! You and these brave heroes have your own destinies to fulfil. This last act of service...is mine.
Kadghar: You will not be forgotten, brother.
Illidan: I must be forgotten, Khadgar! If the world is to live free from the tyranny of fear, they must never know what was done here this day.
Illidan: Tell them only that the Demon Lord is dead... and that Illidan Stormrage... died with him!
The Demon Lord: Now go! Leave this place, and never return!