My thoughts tho, but we saw him getting all worked up when seeing Naruto, and I dont think Kishi showed us that just so we know Sasuke is weaker... I think he just got motivated to show what he's got. Yeah, he doesnt know senjutsu, but he has EMS and Obito is about to try and do an infinite tsukuyomi so I bet Sasuke will be the one to at least slow him down or something until Naruto and Minato can beat him up.
Perhaps Im wrong, but we havent seen Sasuke doing anything for quite a while, its about time he does something cool again lol. I dont believe he is just gonna watch the whole fight.