For many of us, it is kind of a common reasoning now that Madara is going to be rofl-stomped at his current condition by the remaining characters + buffed Naruto/Sasuke. Madara did not even fight at his full potential to begin with (which could explain his lack of ability usage), since Obito "exported" his left eye to the Box Land.
It is a common sense now that Madara requires a power-up to even pose a threat to Naruto, who is by now playing soccer w/ Madara's most powerful weapon (Black Spheres).
Now, what is the most prominent, existent, possible, and "down-to-Earth" power-up that is available? In my opinion, that is obviously the return of the 2nd eye, that belongs to Madara.
Sadly, that is also the most RETARDED event that could possibly happen.
At the current moment, the Alliance is at the perfect situation where they don't even need to worry about Madara's plans succeeding. Madara desperately needs his other eye, and the eye is at the perfect, UNREACHABLE location that is inaccessible to everyone but Obito and Kakashi (and Kakashi's eye is almost gone blind).
In addition, almost all important characters are AWARE of that situation, including most imporant Kakashi/Obito. They seriously only need to run away or destroy their eyes, therefore forever denouncing Madara a FAILURE. Or they can go even an easier route, Obito or Sakura just need to slice the Rinnegan eye inside Kamui, and Obito is in control of his body (and who the hell ported Naruto out of Kamui?!)!
I am going to flip the @#$% out if Madara gets his eye, because that will deem the protagonists as the most stupid, worthless bunch ever, that failed in the most advantageous position.
I assume Madara could potentially catch Kakashi, kill him, rip his MS Sharingan out for himself and warp Obito back into the regular world, but another character death is obviously unlikely (Gate of Death MY ASS!), and Kakashi's MS is already almost gone useless it seems.
What are your opinions, expectations, and alternative power-ups for my boy Madara?