Well, dunno what happened to Imperious, but to Imperius well, he's dead, you see that body on the ground before you go kill diablo? That's him, watch your cutscenes next time.
Adria isn't seen after the act 4 cutscene and is most likely our content for the expansion, sounds good to me.
Leah, well, she's dead. You know that red smouldering thing you see on the ground after you killed diablo... that's leah. Seriously man, do you watch the cinematics, like, ever?
Oh, you know the black soulstone, you know when Diablo's corpse was falling off the pinnacle of heaven, y'know, in that cinematic and it fell to the ground somewhere... yeah. Up for grabs. IMAGINE NOT CLOSING THE ENTIRE STORY LINE FOR A GAME WHICH WE ALL KNOW WILL HAVE AN EXPANSION AND PROBLY A SEQUEL. /palmface.
Oh, and for those finding 'Kulle Story Bro' hilarious, go check your hardcore act 2 achievements, and you'll find it right there. >.>