But what makes you think that Madara will not disappear? The fact that he's an Edo should not exempt him from leaving the battlefield, along with the others. Muu was only an instrument in summoning him, just like Pakura of the Sand and Gari of the Stone who brought up the rest of the last generation of the Hidden Mist's seven swordsmen (
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and
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).
The latest manga showed that those who were already sealed are affected the ending of the edo tensei, as those who are still fighting or like Dan, who was kept inside a barrier (too bad he doesn't get to see Tsunade before he leaves, though). So I assume that Madara will be surprised and severely disappointed (along with those who are rooting for him and calling it a lame end) when he starts breaking up.