Seeing as how we are already six chapters into the volume, I feel like the war will come to an end by the next volume. From What I've notice while reading the other chapters.
Volume 67 so far:
(Note it's not in depth, just summarizing the chapters in one sentence)
Chapter 638: Shows everyones reaction to Obito becoming the jinchuriki.
Chapter 639: shows The Edo Hokages using strategy against the tentails jinchuriki.
Chapter 640: Minato saves Naruto and Sasuke/Obito regaining control as The Sage of Six Paths (Incomplete).
Chapter 641: Minato, Tobirama, Naruto and Sasuke lay a mark on Obito.
Chapter 642: Obito explains his powers to Minato, Tobirama, Naruto and Sasuke, Yin Kurama appears.
Chapter 643: Senjutsu is Obito's weakness/ Yin Kurama (Minato) and Yang Kurama (Naruto) fist up.
What I see happen in last four chapters of Volume 67:
Chapter 644: Naruto's new Tailed Beast Mode, powers are revealed. Minato assists his son to destroy the barrier, and teleport the tree to another spot then return, Gokages/Orchimaru, Suigetsu and Karin appear at the end of the chapter.
Chapter 645: Gokages either assist Hashirama against Madara, and Orochimaru's team assists Sasuke against Obito. Tsunade takes Sakura's spot for healing as she steps back in the battle to assist Naruto. Possible NaruSaku moment as to what some people are saying.
Chapter 646: Both battles take place, and the alliance assist one of them. Madara annnounces that he's about to use his trump card.
Chapter 647: Madara uses his trump card, and how it can be used against Obito.
Trump Card Theories:
1. Edo Rin is one that people keep bringing up. I think it kinda makes sense because We've been seeing Rin panels for the bast few volumes. This would cause Obito to react to this (Yeah I know he loves her that much) This could be one of the parallel possibilites between Sakura and Rin.
2. Some kind of Uchiha jutsu asspull that we never heard of before. At this point I wouldn't be surprised if he uses that to somehow extract the tentails from Obito to become the jinchuriki by sacrificing one of the foder.
3. It's the same as one except like Madara, Rin is enhanced with Hashirama's power maybe. That could be asking for too much,but I see him controlling Rin to fight against Obito, and that could possibily get Madara to become the jinchuriki by sacrificing a foder.
Although it would kinda be like how 637 ended with Obito becoming the jinchuriki, but I'm leaning towards #1 because it would make more sense from a story perspective. At the same time it's like really that's how Obito was defeated. Again their just theories so let me know if you guys have something different in regards to Madara's trump card.