They did in journeys

As well as the other main alola characters

Yeah, alot of old companions came back

Dawn, Serena, etc

Ik but it just seems righy

He's probably Goh's son

But having Ash's and Goh's children as protagonists makes sense but also ruins the purpose of pokemon

No he can't be go son because one of the riders for Pokemon said that Ash is forever 10 and go is the same age around as Ash so you can't really have Roy be Goh's Sun if Ash is forever 10 years old because they're both the same age

There could be a time jump. Technically we dont have a confirmed year for ANY of the series happening at any time.

Maybe the Ho-oH that passed in the first episode granted him to be 10 years old forever and only grow up when he reaches his dream