He doesn't need any more power. He does need to figure out some new attacks, though. I don't mean more powerful attacks, but attacks that use his current abilities in different ways.
If the series is going to end with Naruto and Sasuke having an epic battle, a la Hashirama and Madara, then Naruto currently doesn't need to be any more powerful. Of all of the Uchiha characters that are still alive (or recently died), Sasuke is by far the weakest. He probably couldn't even tangle with Kakashi now that he has figured out Kamui. In other words, Naruto needs to give Sasuke some time to catch up in order for the ultimate showdown to be even worth it. Otherwise, Naruto is just going to mop the floor with Sasuke and forcibly take him back to the Leaf Village.
Looking at his recent history, Naruto has soloed Pain, who crushed the entire Leaf Village without even breaking a sweat, he soloed all of the Zetsu clones that were killing all of the Allied shinobi, he went up against most of the other Jinchuriki and "defeated" them, and he is the only reason that Bee, Kakashi, and Guy are alive right now against Obito and Madara. He is going up against the arguably the second most powerful shinobi of all time (behind Hashirama) and his apprentice of sorts (Obito), and he isn't dead yet. That is an impressive feat in itself, but I'm sure that he is going to top that and beat them with some variation of the Rasengan/TBB.
Which brings up my initial statement. Naruto is pretty much god-like right now, and yet the vast majority of his abilities comes down to Shadow Clones and the Rasengan/TBB. He needs to learn something else. For everything that Sasuke lacks in strength, he makes up for in versatility. Sasuke has Genjutsu, fire and lightning techniques, Amaterasu, Susanoo, can use a sword, and is extremely fast (even though he tends to be slow and methodical in his attacks). Kishi need to balance them out by making Sasuke more powerful and having Naruto learn a new technique or two.
