Im assuming we can expect those three in Battle Tree aswell as people like Lance and Alder but do you think people from region that had few champions can appear? So in this instance Wallace and Iris?

Also rivals. We have generation where there's just one like Blue, Silver or Barry but there are also ones with few rivals. Unova had N, Cheren, Bianca and Hugh. What about them?

I dont count Shauna, Tierno and Trevor because despite popular belief they arent rivals: only Serena/Calem call us their rival. The other three are just friends/companions who very rarely battle us.

Thoughts?

Im not even listing gym leaders because they didnt show any