1-Alain returning as a PWC opponent in the Hyper Class and Ash finally defeating him. Seriously, Ash needs to finally win against him.
2-Ash visiting his Oak's reserves and using at least some of them (as well as the Alola ones) for the Hyper and Master Class of the PWC.
3-Ash fighting at least Cynthia, if not more/all Champions, before fighting Leon.
4-Greninja rejoining Ash for the latter stages of the PWC.
5-Gible coming back and evolving into Garchomp, for DP remake promotion reasons it could happen.
6-Most if not all of his past companions coming back or at least making a cameo to see him in his final fight vs Leon.
7-Paul coming back as a PWC opponent would be amazing too.
8-Gary coming back for a research focused episode and having a friendly battle with Ash for old times sake.
Also, I think we'll see a rematch between Lt.Surge and Ash (Raichu vs Pikachu) for a later PWC battle, given that they said Surge was away training and that he would be happy to hear Ash has gotten stronger. I think that's foreshadowing for a future battle.
2-Ash visiting his Oak's reserves and using at least some of them (as well as the Alola ones) for the Hyper and Master Class of the PWC.
3-Ash fighting at least Cynthia, if not more/all Champions, before fighting Leon.
4-Greninja rejoining Ash for the latter stages of the PWC.
5-Gible coming back and evolving into Garchomp, for DP remake promotion reasons it could happen.
6-Most if not all of his past companions coming back or at least making a cameo to see him in his final fight vs Leon.
7-Paul coming back as a PWC opponent would be amazing too.
8-Gary coming back for a research focused episode and having a friendly battle with Ash for old times sake.
Also, I think we'll see a rematch between Lt.Surge and Ash (Raichu vs Pikachu) for a later PWC battle, given that they said Surge was away training and that he would be happy to hear Ash has gotten stronger. I think that's foreshadowing for a future battle.