Why would Lord Orochimaru fight with Sarutobi sensei? They have nothing to fight about and had a fairly good mentor student relationship. Lord Orochimaru, this chapter, essentially gave up any ill feelings he had towards the leaf village.
The arc can really only end with Naruto and Sasuke, vs Madara. Madara has both Rinnegan and Sharingan and can rejuvenate, while, at this point in time the revived kage dont have as many buffs applied to them. Unless Lord Orochimaru can use debuffs on the field or some jutsu's with wide area of effects for targetting multiple character units, then, really Madara will easily have an simple time handling any opponents. If even the allied shinobi forces jutsu wasn't enough to stop him...could first and second hokage really be enough? Konoha's Yellow Flash seems like he'd go to whichever field has Naruto, would be silly for Kishimoto not to give us screentime with both fighting together. Bee seems like he'd be captured to increase the tension and drama, and Kakashi-sensei and Obito would die hand in hand at the same time pushed to the limits.