what reaction do you think sasuke will have to seeing naruto's tailed beast mode? i think he will be very impressed but wont react out of character!!!!
I think he's going to acknowledge Naruto's skill advance even more than just sayin' "so this is the Kyuubi's state with it's chakra controlled". And I think he'll get some power-up somehow, to be equal to Naruto. After all, Naruto has the Sage's body and Sasuke - his eyes, they have to be equal one way or another in my opinion.
Not only Sasuke, the whole alliance except Gai and Kakashi has never seen Naruto transforming to Kurama. So I'm expecting some reactions at least from the alliance. Sasuke might not show any interest as always but we've all seen his analysing look towards Naruto's KCM, so he might make another internal assessment..