i also think that oro killed sai's brother. I just hope that kishimoto doesn't kill the upcoming climatic scenes by filling it with flashbacks. This is a breakdown of what i think is gonna happen in the upcoming fight. Firstly, they 're gonna separate into two group sakura vs kabuto and naruto vs oro. It doesn't really matter about the others , but perferably sai with naruto.
Things to expect from naruto
1. new kage bushin combos
2. stronger rasengan
3. classic jiraya moves : needle guardian , frog stomach * not really sure about this one but would be really cool.
4. Kyubi release, better control of more then 2 tails i think he's gonna release up to 5

I think that this fight is gonna be like the naruto/sasuke vs haku battle. Where they are both fighting independantly and then sai gets injured/ dies trying to save naruto . Allowing naruto to snap and completly trash oro. Until sasuke, which has been watching the whole thing comes to save him, right before naruto's "that jutsu" can connect . Then sasuke becomes all envious, wanting to fight naruto to see how strong he has become. But oro who has always feared naruto's relationship with sasuke doesn't want anything clouding his mind before the transfer can occur, and they all flee.