Uh its obvious isn't it?
Seeing as Kishi really likes having DBZ with Ninjas, Naruto will turn into his 5 tails form (which unlike the 4 tails form is under his complete control, and doesn't harm him at all, as per DBZ laws) and proceed to kick everyone and anyone's ass.
(For those who don't get the DBZ reference, we get Super Saiyan 1 => SS2 => SS3 => Giant psycho uncontrollable gold monkey form => SS4... which is oddly reminicent of 1 tail => 2 tails => 3 tails => psycho 4 tails => ?)