Sasuke can never ever catch up to Naruto ones Naruto becomes the SO6P,its time you reconciled your self to the Facts Naruto is the child of Prophecy,the savior of His word and as The Tail Beast acknowledge the successor to the SO6P. Admit it now and save your self the hard aches that are sure to come.
Naruto being the child of prophecy has nothing to do with power levels. The prophecy said he would bring great peace into the world, not that he would be the most powerful ninja in existence.
Naruto parallels both the younger son and the Sage. The younger son was meant to succeed his father. Naruto will be the younger son that succeeds the Sage. He will have the powers of the younger son only. You don't need all of the powers of the Sage to succeed the Sage. Why? The Sage choose his younger son (who just had the body part of his powers) to succeed him. He didn't then tell the elder to surrender his eye powers to the younger. The younger was going to succeed the Sage without those powers. However, something went wrong. It was presumably the elder's rebellion. This is why we never hear of the younger as his father's successor. However, this part of the story hasn't been sufficiently explored to know for sure.
Becoming the Sage's successor means he will correct the mistakes of his previous Sage, finding true peace and having the tailed beasts like in harmony with the ninja. "Surpassing the previous generation" isn't about power. It's about building on the base the previous generation has left and building it better.
If Naruto becomes the Sage, then Sasuke's character was entirely pointless. His purpose was to be the yin while Naruto was the yang. Now, Naruto is all of a sudden both thanks to the Rinnegan. Sasuke is the second most important character in this story. He will have a hand in the conclusion, as he has been relevant for the entire story. He is too an important character to be forgotten by Kishimoto. Finally, if Naruto becomes the Sage than the theme about teamwork is broken. Naruto won't need a team. He'll just fix the world problems himself. With that power he might not even need tnj. Naruto having all of the Sages' powers would be a
horrible ending.
my ideal ending: Is Naruto has younger son's powers (yang), while Sasuke has the elder's (yin.) Naruto fixes the worlds problems by convincing others to embrace peace. Sasuke functions as a yin adviser to Naruto. (To make balanced decisions, you need yin and yang. Sasuke has yin but not yang. vice versa with Naruto. This is why they need to be a team.) Naruto brings peace to the world. By doing so Naruto succeeds and surpasses the Sage by doing something the Sage could not. happily every after.