Sakura. Assuming that Naruto, Sasuke, and Sakura become like Jiraiya, Orochimaru, and Tsunade respectivly. Sakura at some point will have to advance to the same level as Naruto and Sasuke. In doing this, she would have to advance atleast twice as fast as both Naruto and Sasuke, and theoretically if she kept up that pace, then at some point she would surpass Naruto and Sasuke to the extent that they would never be able to catch up save for the fact that Naruto is the main character and Sasuke is Kishimoto's favorite (and Naruto's rival). You could say that Sakura still doesn't have alot of potential, she will just reach her maximum at a fast pace, or that someone else could become the next virtual Tsunade. Either way, at some point if she does catch up to Naruto and Sasuke there is no mistaking that atleast for that arc, reguardless of current level, Sakura will show by far the most potential seen in the entire series.