Since people felt the need to zero in on it, does anyone really think were ever going to see Ash become the strongest trainer in the series? Because apparently that's all it means to be a Pokemon Master. So thats what his dream is then. Because this STILL brings us back to the downgrade Ash recieved in Best Wishes. He was closer in Sinnoh to achieving his dream than he ever has been and now he seems like he's farther than he's been in a long time. In a way even farther than he was back in Kanto, because we've seen a better version of him and now were stuck with this newbie.
I'm sure kids watch the show for more than Ash. LOL, The difference between DBZ and the Pokemon Anime is like the difference between Heaven and Earth.
I can agree that there's no great financial gain that'll take place by getting rid of Ash, however I also don't see the show losing a lot of fans or suffering because of it, because most people are either sick of Ash as he is or completely new to the series and can adapt to any main character they see.
I think Ash has been kept around because the writers have never even really tried to finish his story. He's at least going to win a League before he goes. Anything less is just disrespectful to fans of the show. If the writers ever have him win a competition there's no doubt in my mind that he'd leave. Let's not overestimate how popular he is. I'm sure there would be plenty of people angry at his death, but I highly doubt it would be the entire fanbase (Or even half) I got into the anime after playing the games and i'm sure the same can be said for many others. I don't think Ash is the one thing holding the show up. (The anime has a lot of flaws, but thats not one of them)
Overall, there are numerous characters who have come and gone without ever completing their goals. If that was going to be a staple of the series (Like Dreams are for One Piece) then numerous other characters would've been shown completing their goals. I think its apparent that the most important thing in the show is the adventure itself. This is why I didn't ever think Ash would become a Frontier Brain. That ends the adventure.