Two predictions: Orochimaru or Sasuke will defeat Madara
These two predictions are based on recent events and some old history.
The first prediction concerns the outcome of a possible confrontation between the current Orochimaru and the current Edo-Tensei Madara. I believe that Orochimaru would quickly win such a fight.
The reason is simple: the remote-control tag that Kabuto has embedded in the body of Madara.
Kabut did not have time to use it, but Orochimaru is sure to know how to use it, and this would be the first thing he would try in a confrontation with the Edo-Tensei Madara.
The tag used by Orochimaru and Kabuto is not the same as the Edo-Tensei. If you go back and look at how Orochimaru created the first Edo-Tensei in his fight against Sarutobi then you will see that he first used the Edo-Tensei, then inserted the tags.
The tags must be working using a different principle. And this means that when Madara cancelled the Edo-Tensei contract, he did not inactivate the tags.
And, I think Madara does not know about the tag's existance. Kabuto never tried to control Madara, he gave him complete freedom. So, Madara would be completely surprised by this technique.
The second prediction concerns Sasuke's confrontation with Naruto.
I believe that if Sasuke joins the fight between Naruto and Madara, he will be faced with a dilemma: which should he support? I think he will choose Naruto. Here's why:
Sasuke's goal has always been to resurrect his clan.
Even when he decided to destroy Konoha, Sasuke refers to his original ambition.
However, if he joins Madara, than this ambition cannot be completed by himself. Madara may destroy Konoha (along with the whole Shinobi world), but if Sasuke supports that goal, he will not realize it himself. This is one of Sasuke's main character traits: he is an ambitious, proud, selfish and independent person. I think there is no way that he would let Madara take the lead.
More importantly, while Sasuke intended to destroy Konoha, I think it was just a first step. He wanted to really recreate his clan later, after freeing it from relations with Konoha. This would be out of the question if Madara succeeds.
Finally, Sasuke may realize that Madara represents the worst things about the Uchiha. On the other hand, by joining Naruto and destroying Madara, Sasuke will be able to revive the Uchiha on his own terms, and to give them a new, good position in the Shinobi world.
So, these two predictions can be summarized like this:
1) If Orochimaru takes part in the fight, he will defeat Madara using the remote-control tags
2) If Orochimaru does not fight, Sasuke will help Naruto to destroy Madara.