Well, Sasuke might learn from his future self about his family and how his actions in the future have either helped or hindered the Uchiha legacy. Sakura could discover if she has achieved all her medical and combat goals. It could be a story full of revelations, self - discovery, and perhaps some warnings about the future.
The encounter with their future selves could also lead to some tense moments. For example, if their future selves tell them about some upcoming disasters that they are unable to prevent. It could also be a chance for them to correct some mistakes they are about to make. They might see new jutsus or skills that they will develop in the future, which could inspire them to train harder in the present.