Originally posted by: Neji-Aniki-sama
And don't give the me line: I am not going to kill you now, but I will kill you later.
Either you kill or you don't, and if you really have power to do it, don't make threats that only can come true in the future. If you are going to do something, just do it. Talk about what will happen in the future is as useless as argue about if they fought who'd win, the 4th or Itachi, Shika or Haku?
Itachi didn't kill Kakashi because he wanted Kakashi to learn Tsukiyomi and pass it on to Sasuke.
That's my theory anyways.

Same thing when he pulled it off on Sasuke later on. He didnt' kill Sasuke because he was merely showing him the ability.

Who knows why Itachi is babying his little brother. Maybe he has some plan for him later.