Spoilers tag because i will likely mention /reference various spoilers liberally, even if the subject is not directly spoiler-y.
So yeah, on the subject of the old gods: How are they, currently?
After all "They do not die; they do not live. They are outside the cycle.".
1. C'thun: Dead underneath the rubble of Ahn'qiraj, though still more than juicy enough to mutate Cho'Gall severely. Currently next to a gargantuan sword that bled raw power all over the place.
2. Yogg-Saron: Dead, conveniently just after the Lich King constructed a giant edifice made out of his blood right under the place where the Shadowlands are closest to reality. Also the place that literally has its sky ripped open in the upcoming expansion.
3. N'zoth: Lazered to death in his own disintegrating dimension, conveniently making the knife-that-can-contain-void-things unfindable for the moment.
4. Y'shaarj: Dead dead, by the hand of Aman'thul, titan of time. However Argus' fight shows that his power is far from absolute or failsafe, so we might get a "terror from beyond time" sorta return so that we can face him in the flesh.
5?. Atath ("Xal" basically means "weapon" in Shathyar): The thing that-was-in-the-knife that is m.i.a. after delivering us so that N'zoth may peer through our eyes.
Plenty to go on about, but let's focus on their potential appearances in the Shadowlands, with Yogg-Saron being the most natural.
Now Yogg-Saron, as you may remember, styled himself the god of death, appeared as pretty much only maws (curious innit?) to us, broke his chains on his own and then mysteriously got offed by a bunch of random dudes on a side-quest, whereas our other faced unchained old god was much more, shall we say, flamboyant and chatty.
So i'd say it's pretty clear that Yoggy's still "alive", if it can ever be called that, and that he's been messing with the Shadowlands for a long time now.
He seems a very likely candidate to be one of those who was part of the Void Lords' "open armed" embrace of the minions of death, as per the message relayed to sire Denathrius in one of the more recent bits of lore. In the same message it is acknowledged that as the void lords observe and obsess over their thousand truths they may in fact be seeing through the deceptions of death, and thus may be the actual beneficiaries of it all.
Either way a clear cooperative effort has existed, and one has to wonder what becomes of it in the upcoming expansion, as their past cooperation would explain the long held view that shadows and necromancy are inherently intertwined, and considering Yogg-Saron's propensity to cast curious plagues in his encounter he may have been the source of more than a few powers the scourge employed, and given that by the time of WotLK there had been animosity between the scourge and Yogg-Saron that may explain the disappearance of the obsidian destroyers from the scourge's arsenal, as well as the curiously reduced incidences of the formerly extremely dangerous and virulent plague, despite a great many different varieties of it existing now (thanks to, among others, Sylvanas).
Of note too is that Sylvanas died on a spike of Saronite right under the weakened sky of Icecrown, and that she's been a lot more genocidal since then (Gilneas comes to mind, among others).
So we have then, at the end of WotLK:
- One dead death god who does not die, whose blood has formed a curious edifice right under the Shadowlands
- One dead jailer of the damned, who has curiously been keeping the scourge passive and entered in to conflict with Yogg-Saron
- One dead leader of the Forsaken, her purpose fulfilled, only to curiously re-emerge with a much less inhibited genocidal bloodlust
Frankly it seems to me that Sylvanas has been posessed by Yogg-Saron, much like Atath posessed that other elf in the quest it sends us on. It seems that the pact between the Jailer and the outside force is not necessarily between Sylvanas and him, but rather between him and Yogg-Saron.
It might also explain the odd behaviour Sylvanas exhibits from time to time, as old gods are known to twist emotions and thoughts in what direction suits them. It would also explain how dead souls empower her, as old gods have been shown to be fond of consuming them, and it might explain her apparant view of herself as the jailer's equal - that he is something she cooperates with, rather than serves.
It would also make Arthas more of a victim of circumstances, and one has to wonder how Bolvar fits into all this, but even Yogg-Saron alone can easily obscure much due to the nature of his power.
That's my take on it right now anyway, subject to change as all speculation, and i'm curious about what you guys think about this one