it looks like sasuke might have the 6 tailed beastSomehow it looks like the Kyuubi , but then again it can be said that it is Madara who is controlling him too.
First reason , Madara is the only one able to control the Kyuubi now. Therefore , the kyuubi manifestation behind Sasuke.
Second reason , Madara is the most likely person at trying to start a war. With the plans that he talked about with Zetsu.
Third reason , if there is a person able to control Sasuke , it is Madara.