http://www.mmo-champion.com/threads/...Burning-Legion
In this post there was some nice discussion about this topic, make sure you take a look.
I had stated my thoughts already on this matter, but to make a brief resume: The Legion is way bigger than we thought, and in Argus we will see just that. Even after we defeat the Legion there, it woulnd't be a huge problem for them. They have conquered and destroyed planets for millenia, so they could have other generals like Archimonde and Kil'Jaeden everywhere (even more powerful).
Focusing on the final boss, it's certainly a true enigma. Sargeras is out of the question. We are going to defeat his Avatar in 7.2 so having him again (or his real form or any kind of form/avatar/whatever) in the next tier sounds unlikely for me, and he's planet sized and the most powerful being of the universe so we shouldn't be able to touch him. Same applies to Kil'Jaeden and Archimonde, maybe they make us fight them together in the 7.3 raid but in no way they're going to be the final boss.
I found in this post two nice theories that I would like to comment:
- Many people say that 7.3 patch might not contain the final raid of Legion. I think that it's safe to say that 7.3 will be the final ''big'' patch of Legion, because, where else we could go after Argus? Another planet that we haven't heard about? Who would be the final boss of the Argus raid then? and of the one after that? It could make sense because like that they can built the final boss of Legion a little bit, because allow us to kill Sargeras on 7.3 withouth seen him or interacting with him in any way wouldn't make much sense to me.
I read Illidan's novel, but in this extract that you posted I found something quite interesting that I didn't realise before. It says that ''Illidan Pure Version'' (or whatever way you want to call him) is fighting demons and the void, but highlighting more the Void, making them the main enemy.
This is disturbing, because it seems to me that the demons and the void are fighting together against us. Shouldn't the demons, if commanded by Sargeras, focusing in the biggest threath, in this case, The Void forces?
I thought that after this expansion Illidan would become the ''King'' of a small portion of the Legion armies after defeating them in Argus (he had commanded demons before, and the DH hero has demons at his command). But after reading this extract it seems clear to me that the Void will take control over the demons in one way or another.
So something like this could happen: we go to Argus and defeat the Legion there, but Sargeras manifests himself, and we haven't a chance against him. But a Dark Titan / Void Lord appears from nowhere, Sargeras fights him but eventually he falls, but before that he recognizes our power and sacrifice himself to give us time to get the hell out of Argus, closing the portal after us, and he dies saying something the lines of: ''There is no hope'' or ''now you're the last hope of the universe'', depending on how dramatic you wanted it to be.