I have always wondered something as well....if Tobi is Madara or some form of MAdara or whatever theory there is..then why didn't Tobi already know how to end the Edo Tensei seeing as how Madara apparently did..and knew this before he died..
He could have been planning on betraying Kabuto all along, and knew that at anytime he could take him out. The plan could have easily been *Tobi thinking*.. "I'll let Kabuto Edo Tensei "Me" and then break the Jutsu, thus giving me a Eternal body with unlimited chakra".
Or
Tobi is not Madara, and actually had no idea how to break the Edo Tensei, and still leaves the question..just who the hell is Tobi..I am leaning towards someone we would never think he could be, MAYBE Sarutobi or Tobirama...but who knows