Good theory but I hope you are wrong.
if thats the case then we still have yamato as a trump card. Maybe him and the statue of the 1st will fuse together or some shyt and battle with the real deal madara
Man, I just feel like we have too much unfinished business with Madara for him to just disappear. We still don't know:
1. What Madara's connection is with Tobi
2. How he survived his fight with the 1st Hokage
3. What he did after that
4. Who came up with the Moon's Eye Plan (Madara mentioned it too; so I'm not sure if it was his idea or Tobi's)
5. How Madara got the Rinnegan in the 1st place?
6. What Madara's relationship is with Nagato/Akatsuki (remember, he was expecting Nagato to revive him)
Madara has lots of unfinished storyline business. I just kind of feel like that needs to be resolved before he disappears from the story.