We really are not going to solve this conclusively one way or another until we find out for sure, which I would say kudos to Kishimoto for writing it in a way that has given rise to two strong arguments.

In addition to the points made above, I would once again say that the continuing presence of Madara with the departure of the other Edo Tensei fighters would make no sense if he does not have a continuing influence on the story apart from hax powers. We know the Kage's can't defeat him now, the only way he could go is if he finds emotional peace. That sort of thing could happen if his brother were still about and he could get some connection from him. Unless of course Kakashi/Tobi Kamui him to another dimension or Madara dissapears after achieving peace in a meeting with Sasuke, his Uchiha heir.