There's no way Itachi left Madara for Sasuke, he didn't even want Madara to get in contact with Sasuke(!) and therefore planted the Amaterasu trap in Sasuke's eye. He feared that his plan would fail and that Sasuke would be tainted by Madara, and as such made a back up plan by giving Naruto a crowjob. I repeat, there's no way Itachi would leave the job for Sasuke if he had a chance of preventing it, that much is painfully obvious. Itachi loved Sasuke more than anything, more than Konoha, he would
never take the risk. Itachi is smart and rational, not stupid.
I don't know how many times I've said this, but it's obvious that Itachi had no clue how to kill Madara and as such didn't even attempt on taking his life. I personally can't understand how Itachi didn't know about Izanagi, but I don't think he did. In fact I think that's what saved Madara from his Amaterasu trap, and that's what Madara referred to as
"kept secrets from Itachi". If he didn't use Izanagi there, it must have been a standard suck in the flames no jutsu, meaning Itachi didn't even know about his warp jutsu. Either way the point stands, Itachi didn't know how to kill Madara no matter what he knew and didn't know about him. So now you ask, why didn't Madara just take the fight to him then? Because he knew that Itachi would eventually die anyway. He had full knowledge of Itachi's plans and knew that with patience he would get rid of him for free, so why take the risk of fighting him? Besides he needed what happened to happen to convert Sasuke to his cause.
Anyway this fight has been predictable to happen since the tournament's beginning and I've already given it a load of thought. Madara should take this, how? He outlasts Itachi easily. Itachi is not a chakra powerhouse, he can't keep up Susano'o for too long either going by his final fight. If he uses it when he's fresh at the start of the fight, he'll probably be able to maintain it longer, but it's all useless. We have no proof that Totsuka will work on Madara, and Madara is freaking fast and keeps appearing under/behind people to suck them up like he did against Torune. That's all he would have to do. Minato got away because he had a teleportation technique that is even faster than Madara's, Itachi has no such technique and would get wtfblitzed and sucked up into Madara's dimension. Susano'o is useless, Madara would juse appear
inside it.