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Posted by Sakura might even be Obito's Yahiko.
With that I mean..
Nagato went evil because of a lot of things, but Yahiko was the primary reason. He found hope in a "new" Yahiko, Naruto. Obito might do the same, maybe through Naruto's words? Sakura is capable of TnJ, but I think this is Naruto and Obito's thing.
In my opinion, the TnJ will involve; Naruto being successful in his dreams and Sakura, the "new" Rin. The two are connected because after all, Sakura is the girl of his dreams.
Not so soon. The last 100 chapters have been for two days. The war is going slow in terms of timeline.
And btw, how are the Kages going to get inside the barrier? They'll be trapped outside. : (
If Sakura does join in the TnJ, Obito will know that--just like Rin--she loved someone else and use it against Naruto. But then this could also set up a scene where she can counter Obito's claim that "a girl's feelings can change" and that you'd never know, maybe Rin fell in love with Obito before she died (Kakashi could confirm this as well when HE FREAKING GETS BACK FROM CUBE-WORLD) and through that she could hint and FINALLY get Naruto to see and believe that all that she's said back in the Land of Iron were very much true.
I don't blame the dude for doubting though, he has his reasons from his love for her being sensitive, used to and resolved with the fact she may never return his feelings all the way to not really absorbing the concept of a shift of feelings that deep, since he can't do it himself.
)
damn. do i know how to pick 'em! 
in fact.... was it even an "interaction" to begin with? all was there was Sakura calling "sasuke-kun!", him ignoring the kitten out of her as always, and the rest of the dialog was only between Naruto and Sakura. 
Plus, that smile of Sasuke? no threat at all. It's part of the plot and her character development. Remember, her resolve was for her to have BOTH BOYS--meaning Naruto AND Sasuke--to acknowledge her. Naruto already acknowledged her YEAAAAAAAAAARS ago. Last chapter was only a reminder that he already has, and is proud of her. Now it's sasuke's turn to give a kitten about his teammate.
