I just want to comment something.
All episodes of the series have been practially continuous. I mean, each time ended a Gen's journey and started a new one, there was no time resting. For example, the same episode where he returned from Unova, he went to Kalos. However, there's an exception. After Kalos, Ash spent an undeterminated time in Kanto before his mom and him won the journey to Alola. There's an unconfirmed theory that, during that time, some things happened. One of them was the potential return off-screen of some of Ash's old Pokemon. It was "uncertainly confirmed" in SM042, "Alola, Kanto!", when Ash's Squirtle (and the whole Squirtle's Squad) appeared at Oak's Lab. And I believe Ash's Pidgeot also appeared, alongside a Pidgeotto and a Pidgey.
So, this is unlikely, but do you think we will see one of Ash's old Pokemon returning off-screen in the Hoenn's Tournament? Even more, do you think Squirtle could return, evolved as a Blastoise?