here's my theory it's a bit long winded but i think it makes sense:
-Ash will win the sinnoh league in a cataclysmic battle against paul
-The Sinnoh Elite Four challenge him to enter the champion's league
-Ash defeats Cynthia
-The anime's story will shift focus to another trainer(hopefully a girl; possibly the main girl character from FireRed and Leafgreen)
-While the new trainer(let's call him/her "X") participates in the league of their region, Ash beats the leagues of Kanto,Johto, and Hoenn
-X will win his/her league
- Ash and X will enter a new tournament showcasing the best trainers around the world
-Ash and X face off in the series' true final battle
-The series will close explaining what happens to all the characters afterwards
- And hopefully, Nintendo will do an Anime adaption of the Pokemon special manga series