Ohhhh! Interesting question.
With Haikyuu characters, I can see a lot of them staying in Japan, save for those boys who make the national team and travel with them but even then I think they’d return to Japan.
With KNB, I can see a few more of them heading out into the world especially the GOM’s because the majority of them want to continue in basketball after they graduate so I can see them taking offers if they get them.
Most likely Akashi would take over the business eventually, so he’ll probably get whatever business degree he needs and stay in Japan to learn what he needs to do for that.
Thanks for the question, it’s fun to consider what’s happening after the anime/manga wraps up.
What do you think they will do?