The show followed him for 10 years, ended with the Battle Frontier, where he was offered a chance to be the Frontier Brain (read: King Gym Leader). He decides to keep getting stronger, gives all his Pokemon to Oak, then takes Pikachu and Aipom on a boat.
Then in the new season (Diamond and Pearl) it follows just Dawn for two episodes or so, with brief glimpses of Ash looking for his lost Pikachu. They team up, reunite everyone, then Ash forgets everything because he's a faggot.
He was last seen telling Pikachu to use an electric attack on a ground Pokemon, shocked to see that it didn't work. Also Dawn's episodes are all beauty pageants, so nothing ever happens.