So, by now I'm assuming everyone reading this post will have seen the last cinematic.
IF YOU HAVEN'T, TURN BACK NOW IF YOU WISH TO AVOID SPOILERS!!!
Ahem...
So, we see Kil'jaeden effectively face facts that he's a giant D-bag, and basically says he hopes Velen can kill Sargeras. Velen then places his hand on Kil'jaeden, and we see an explosion of light, just as the heroes find themselves back on the Broken Shore.
I'm actually wondering if something "bigger" actually went down here.
Theory #1 - Velen killed Kil'jaeden
When Velen's son died, dude clearly wasn't happy. He says "Tell them... the Light died this day", which is foreboding as hell. Between the "Void Lords", the "Holy Nathrezim", and the fact that the new Naaru is proclaiming Illidan is the "Champion of Light", I've a sneaking suspicion that we may face both Light and Shadow as destructive forces. Velen using "the Light" to eradicate his former comrade in a show of hate could be the first clue that Velen has lost it.
Theory #2 - Kil'jaeden isn't actually dead
Another theory could be that Velen actually doesn't kill Kil'jaeden. We see Kil'jaeden's fel-colored scars fill with holy light before that blinding flash, so perhaps it is possible that Velen removed the Fel corruption from Kil'jaeden. I thought it curious that after the heroes "land" back in Broken Shore, we don't actually see a panned-out shot of them; only their faces. Perhaps, then, a "non-corrupted" Kil'jaeden could be lying at their feet?
Either way, I'm curious to see what Argus holds!