It seems like he's looking for a reason not to crush the Leaf. Or, maybe it's just that he wants to direct his hatred at the correct target. He's not sure who to destroy yet xd
There's been foreshadowing of Sasuke coming back to the Leaf's side. Itachi said that he was leaving Sasuke up to Naruto, and only because he believed Naruto to be the only person who could reach Sasuke.