Sasuke wants to learn everything about the leaf villiages past and the uchiha massacre... No one knows more about the leaf villiage than the past hokages. When sasuke showed oro the scroll, he automatically knew who sasuke wanted to talk to, that means that scroll links them to the people who knows everything. Hiruzen is the man who knows everything about the uchiha massacre, and the hokages in general are the people who know everything about the leaf villiage. That scroll most likely either summons the death reapers stomach or allows orochimaru to contact the hokages in the stomach, there may even be a way to get the hokages out of it, explaining why suigetsu said it might change the outcome of the war. I doubt its the elders because who ever they want to talk to is somehow connected to that scroll. If this theory comes true, that ive had since i first read the oro resurrection chapter it will make the manga become even more epic
