The Sport Based contests could still be a single player. Baseball wouldn't really work, but I think Basketball, Soccer, ect still can.
They said in the Direct that the Galar Region was built by both Pokemon and Humans working together. So a big theme could be that. So instead of using multiple people, they could use their pokemon as partners instead. Similar to how Machoke was a Pitcher for baseball in NImbasa. I don't think baseball could work though.
Sports I think could be included could be Tennis, Basketball, Soccer, Volleyball, Track/Field, Surfing, Skiing, Snowboarding, and Dodgeball. Just some examples that could work with a human and one or two pokemon.
I forgot to add something to the Sporting possibility. The main female in Power of Us, was also a Track and Field character. So there are numerous things in the past that could be hinting at it. Serena was also being pushed to be a Rhyhorn Racer. and we had wrestling.
I wouldn't mind if they replaced Ash, it would be nice to leave him finally, but I don't see it happening, which is why I am assuming. And even though I did say not to bring it up, I will respected how it was said, but I will add I don't think it will be canceled. There were a lot of people who did enjoy Sun and Moon that hated X and Y. So I think regardless, there is a viewing. And pokemon has been pretty consistent staying within the Top 15 from what I have looked at and seen. This will probably be the last time I talk about it as I want to try to concentrate on what could come.