Now that the manga has ended, let's discuss what's next in store powerwise since it iswas a battle shounen manga and we already got and will get more answers to who got it on with whom. Let's see how strong they can get. I know they are already the strongest but since other dimensions/space is a thing they might still prepare for Frieza's/Cells/Majin Buu's attack. Fat Buu already turned Choji's child into chocolate btw so there is obviously the need to get stronger

Sasuke: First of all get Kabuto and go to wherever he learned Sage Mode and perfect that. Maybe get some Juugo cells for extra natural energy absorption. Master the Sharinnegan's Paths which probably include all of Pain's paths and more like Limbo and swap swap no jutsu.
Master all elements whatever significance that may still have.

Naruto: Since he can do a lot of Kage Bunshin he can basically shortcut to whatever he wants to learn, I guess. He has access to all Bijuu and also to the Rikkudo mode which he needs more practice with, especially those extremely OP godoudama.
My personal wish would be for him to realize he is an Uzumaki and learn some of their ancient sealing jutsu.