"Meeting the one who knows everything"
Just wanted to share something which I'm guessing has already been shared/confirmed by many other people, but meh..
The one who knows everything is tied to the Scroll Suigetsu found. It's not a power-up for Sasuke, at least it's highly unlikely.
Read this page
Suigetsu says it's somethin powerful enough for the 'Hawks' to rule the world. So, it's safe to assume, that it's something outrageously powerful. Possibly a person? Or a contract to withdraw the dead from the Death Reaper?
Nonetheless, the Scroll itself is "The one who knows everything".
Sasuke then says there's someone he needs to meet with and that he's "leaving". On the next page, he clarifies that he's talking about Orochimaru.
"Because there's something I need him to do" - My guess is that the scrolls holds a complexity level which proceeds Sasuke's understanding, and therefor he requires Orochimarus aid. The Scroll itself is the key to "The one who knows everything", which most likely points to being a sort of Forbidden Resurrection of the Dead, or at least a way to communicate with them. At least that's the most probable hypothesis seeing as the Age required to "know everything" far surpasses the average lifespan of a Shinobi.
Here Orochimaru asks Why Sasuke wants to meet "Them" for, after showing Orochimaru the scroll. Which ultimately means, they're people. So, people who "know everything" are tied to the scroll. It's not just one person, it's plural "Them".
Here Orochimaru specifies that it's a location Sasuke knows well, which can arguably be a lot of different places, taken into consideration his absence from Konoha for so many years, it's highly unlikely that it's related to any Uchiha-Camp or Shrine located in and/or near Konoha. So right now, they're not heading towards "The one who knows everything", but rather a place where they can use the scrolls content to bring The ONES who knows everything forth.
I hope this topic can put and end to all the Theories about "Oooh Madara/Izuna/SO6P/Obito/Tobi/Nagato/etc/etc/etc is the one who knows everything"!
Bash me all you want, but that's my understanding. A lot of people also missed that it was a plural statement (>>More than one person that 'knows everything'<<), not singular.