Sorry, I meant if there will be a spin-off of some kind. There will be a light novel though, released on August 4 about post graduation: Karasuno sending off Hinata, Hinata's time in Brazil with Oikawa, Bokuto and Atsumu in Black Jackals and more.
https://twitter.com/aitaikimochi/status/1284048348148686848?s=19
I can only find the translation up to vol 5... ( https://www.wattpad.com/story/88151748-haikyuu-light-novels-haikyuu-sh%C5%8Dsetsuban)
Do you know where I can read the rest?
The rest is not out yet :(( https://twitter.com/Haikyu_EN/status/1284036410178142208?s=19

1. No, there is no clear winner between Argentina Vs. Japan. Maybe there will be some mention of it in a spin off or the light novel that is coming out on August. 2. The last page is Hinata and Kageyama on their respective world cup teams. This takes place after the Olympic game. Hinata plays for brazil while Kageyama plays for Italy. Others are also mentioned to play: Yaku for Russia, Ushijima for Poland, etc. Haikyuu is not about who won that's why there is no clear winner. It's about how hinata and tobio will always play together, whether against or in the same team.