Thats the way Itachi fights he is always reserved and never goes all out. Itachi and everyone else expects that Sasuke will eventually surpass him and this is just another test, I hope we'll soon find out for what. Sasuke's fighting style and tactics are obviously heavily influenced by his training with Oro, Kabuto and Oro were the same way. Most of the ninjas in Naruto are too its has more to do with knowing your own strengths and limitations than anything else.

At the rate its going Naruto being taken over by the Kyuubi will literally kill him and destroy his body not just simply release the kyuubi so I don't think thats it.