According to E! Online, we'll next see Castiel in March. As far as Lilith goes, she will hijack the body of a dental hygienist and return to wreak havoc on our boys in episode 18 (this week is episode 13).
Oh and if that's not enough for you, we have a sneak peak from Thursday's episode, "Afterschool Special" that shows a young Dean and Sam flashback:
[video url="/videos/afterschool-special-sneak-peek/" title="Afterschool Special Sneak Peek"] [/video]