Yondaime needed a container for the Kyuubi, otherwise he could not control it. Meaning, Naruto.
Yondaime could've sacrificed his wife, instead of him and became the Akatsuki leader.. and somehow revive her using the powers of the bijuu? Ok, yeah, I don't know.
There is a theory..
A young Hyuuga girl ran away and fell in love with an undercover bijuu. He formed the Sharingan from the Byakugan. Soon they had a son named Uchiha Madara. Madara found out about his father and made a deal with Kyuubi to let him gain power. Shodaime got mad. Soon, Madara found a girl and they created the Uchiha clan. Now, since Madara was made from a bijuu, all the Uchiha had a little "container" inside of them. Itachi was born, and felt restrained that nobody wanted to release their bijuu. He killed them all. Except Sasuke, because he was one of the Mangekyou users that was needed to release the bijuu. Fast forward, Sasuke's curse seal erupts. He gains a level 3 curse seal, and grows wings, hence his heaven seal. BUT he still had his Sharingan. His bijuu blood and the curse seal mixed.. forming the monster that you all saw. Sasuke did not kill Naruto, which means the Akatsuki had to kill Orochimaru to get to Sasuke.. Like you saw the clip in episode 138, I think.
I think that will answer your questions.