Throughout Naruto, when Naruto or Sasuke learns something new or becomes more powerful, they always become equal. For instance, when Sasuke activated his sharingan, Naruto learned to use the 9-tails chakra. When Sasuke learned Chidori, Naruto learned Rasengan. When Sasuke learned lightning element jutsu and combined that with chidori, Naruto learned wind jutsu and combined that with Rasengan.
Now that Sasuke has gained itachi's powers, MS, Tsukyomi, Amaterasu, and Susano, Naruto has to learn something new to compensate for that.
I think that in the scroll Jiraiya sends to Naruto, there is some sort of power about equal to that of the MS and all of the abilities that came with it. There are several possibilities, I think:
1. Secret to the rinnegan (as you might know I believe Naruto will gain the rinnegan )
2. The 4th's teleportation jutsu
3. Something having to do with the kyuubi's power
4. Completion of the rasengan
5. The name of another jutsu that I've forgotten...