Yeah sasuke knows that in about 20 years he is going to kill naruto, and will feel very guilty, so his feelings are true because he believes it badly and this will make him able to unlock mangekyou...
If the explanation for kakashis mangekyou is that 16 years ago a friend of him died I will just puke at that chapter. I suppose that every different mangekyou has his own awakening, or there is more than one way to do it... or maybe itachi just lied to make a fool out of sasuke.