I don't know anything of Kil'Jaden's current status. I remember that when we last left him he was chasing someone down for not doing a favor promised to the legion.. I remember him being really huge (it was his avatar) and talking to someone who was standing on a cliff -- Illidan, I think.
So, if we're against Illidan (or are the Blood Elves still allied to him?), and we're against the Burning Legion, I don't know who we're going to ally, or if we're going to fight it three-way, but it's probably safe to guess that where we find Illidan, we'll find Kil'Jaden.
It'll probably come out in a future content patch, since right now the current status of the lore is that Stormwind is reunited with the troops from Nethergard and the Sons of Lothar, and the new backup is helping explore the world of Draenor which I guess never got explored properly. I do remember a quote (I don't have it handy, though) that all of the heros in the statues in the Valley of Hero's will be found, but Blizzard (probably intentionally) did not mention what status they're in. I think Danath, Kurdran, and Khadgar are accounted for, leaving Turalyon and Alleria to be found.. who will probably be together, considering they hit the bed and made Arator. I think that'll be Blizzard's next move.
I'd consider myself kinda well-versed in the lore already. I played much of WarCraft II, including Beyond The Dark Portal, and all of WarCraft III and The Frozen Throne. Most of the WarCraft: Orcs and Humans lore I've picked up throughout the lore books in Stormwind, and I read "Lord of the Clans". I want to get my hands on a copy of Day of the Dragon and whatever the one was about Khadgar taking up an apprenticeship with Medivh (I think that's the most critical one there is, actually), and then start on War of the Ancients.
Speaking of which, if anyone has any lorebooks they don't want, feel free to mail them to me.
