Kishi would have to pull something out his butt hard to surprise me more than he already did with Naruto. Right now Naruto has tons of practice and battle experience on his side. I don't care how smart Sasuke is suppose to be I don't think that he could just up a nd master an unknown jutsu that would probably take both Madara and Itachi days or even weeks to master.
So right now and from what I have seen Naruto has the upperhand over Sasuke right now not just in experience but also in overall potential. Right now we know that Naruto is the best sensor in the ninja world, best with chakra manipulation, now an ultimate master of Senpo(was already a perfect Sage), and now can use every one of his jutsus with every element including Ying and Yang. I would love to see what a Ying Rasengan or something would like just as much as I would like to see what Sasuke is able to do.
BUT
Like I said Naruto has the upperhand with all the experience he has with not only being a Perfect Sage but also a Perfect Jinchuriki.