Orochimaru is not going to come back into the manga and play any role in it. He was a fun character to watch for a while, but he's gone now. The only role Orochimaru has left to play is a power-up for Kabuto. That's it. He was a power-up for Sasuke for a while, but Itachi got rid of him and sealed away whatever was left. Now it's just Kabuto.
Orochimaru and Kabuto together were pretty smart. They did not know, but had a guess, that the Sharingan turned into the Rinnegan at a certain level. This does explain why Orochimaru was so interested in getting Sasuke's body. I suspect the strategy looks something like this:
1) Promise to help Sasuke kill Itachi. Sasuke wants revenge so bad that he gives his body to Orochimaru for body transfer
2) Orochimaru gets Sasuke's body and kills some of his closest "friends". Gets MS.
3) Orochisasuke kills Itachi. Gets Itachi's eyes. Gets EMS
4) Orochisasuke does ???, gets Rinnegan. Gets Rinnegan power and "unlocks the secrets of ninjutsu".
At the same time, Orochimaru has a separate plan running: Trying to get wood-style release from the DNA of the first hokage. He did experiments on Yamato (and other children, and Danzo) to figure out how to integrate that power into himself.
These things that Orochimaru was trying to do were for personal gain. He wanted to be powerful. He wanted to be recognized for his power. He wanted to be stronger than Hokage, and then come back to get revenge for not being selected as the Hokage. Orochimaru wanted personal power for himself, and he wanted to get revenge on the Leaf village. That's the whole reason why he started the Hidden Sound village, or why he formed a false alliance with the Sand village: To build an army to attack the Leaf village. That's all he wanted.
Madara is a bigger villain. Madara doesn't just want personal power, he wants complete world domination. He doesn't just want revenge (he already got some measure of revenge during the Uchiha massacre, and then made a promise to Itachi not to attack the hidden leaf while Itachi was still alive).
Orochimaru wanted revenge on one village. Madara wants to conquer the whole world.
Orochimaru wanted personal power. Madara wants ultimate power.
In the end, Orochimaru was a small enemy. He basically serves as a counter-example for Naruto, and a focus for Sasuke. Orochimaru wants to be Hokage and the pursuit of power turns him evil. Naruto wants to be Hokage, and the pursuit of it turns him into a hero. Sasuke wants power, and joins Orochimaru, despite the fact that Naruto is getting just as powerful following a better path. Now that Naruto and Sasuke are reaching ultimate power and they are reaching the opposite ends of the spectrum (Naruto is the ultimate good, Sasuke is becoming the ultimate evil) Orochimaru isn't needed anymore.