Board Thread:Naruto Discussions/@comment-25442710-20140926150531/@comment-4688597-20140928200858

JMac14 wrote: @Kamui-Master

Could be... That might explain why Naruto never went into his full Tailed Beast Mode during the battle with Kaguya, Kishi might have wanted to save that form for the duel with Sasuke.

Another possibility is that that thing is a Yang Chakra/Senjutsu form that can only be accessed if you have the Sage's bodily power, sort of a counter to the Yin Chakra/Dojutsu Susanno that is the product of the Sage's eyes.

I think the question as to if Naruto is going to get that mode can be summed up in one word: Kurama. If Naruto gets both halves of Kurama reunited inside of him, Kishi certainly won't give Naruto that mode as Kurama's full form is implied to be incredibly powerful.

I actually really like that idea of it being unique to those with the Sage's body powers (senjutsu or TB chakra) like the Susano'o is with the eyes (sharingan)