I think it will end like this.
Ash will lose again for the unknown time at the league. He heads back to Kanto, to seeing his mother, Porfessor Oak, Gary and all his Pokémon. Arriving at Kanto, his mother's not at home. He decided to go see Oak at his lab, then. In the field, where all of Ash's Pokémon are, a shadow in front of the sun his lookin' at him, just at the right of his mother : his father. They'll meet finally, Ash will say "Father, my dream to become a Pokémon Master is too far away. I'm not even close to him, even since I started my journey.." And his father will answer "Son, you are a champion since you start your journey with your first Pokémon : You are my champion.". A big hug, and all of Ash's Pokémon en reunited. Than, the next day (in the same episode), all of Ash's friends (of Misty to the last one) are there, at Kanto, saying that all their dreams have came true. Ash will say "My own dream, as you all know, was to become a Pokémon Master, was already done since I started my journey with Pikachu. I was my father's champion.", with a misunderstanding of his friends, they'll meet, one by one, Ash's father. After that, they'll all go on a little hill, with a tree, seeing the sunset. After talking a little bit and encounter with the others, Ash will say "Friends, I think it's time to us to turn the page." They all agree with him, stand up, all of them, and make
a group highfive, screaming "Yeah!" all at the same time. Finally,
a "ink" effected screen capture this moment, and the narrator finally says "This day, when Ash discovered that he was already a champion, to his father that he never met with, since he started his own journey with his close partner Pikachu, Ash was happy to be with all his friends. He discovered that a title is not more important than family, friends and companions." A little silence,
with a screen of Ash huging Pikachu, and the narrator follows "As the journey ends...".