No, Ash is a stand alone character, perhaps a counterpart to Red, but not based on him.
I heard Ashton Kutcher wasn't getting over with fans the way Sheen did, but that might not be the case. I don't care for the show either. But either way, replacing the lead character of a show, any show, is a big risk, especially after being the star for as long as Ash has been on Pokemon.
Older DVDs for Pokemon are hard to find. Anime DVDs in particular are disappearing as fans refuse to pay for them and watch them all online illegally. (Best Buy use to have a huge collection of various anime. Went there the other day and the entire anime section was almost non-existent.)
It wasn't a total reboot. Black and White started of with only the new 156 Pokemon, but postgame, some of the older ones were available.
Besides, if they were to replace Ash now, in another 5 years, there would be a demand for another replacement, and so on and so forth. Why create character after character if they are just going to be copies of each other?
Everyone screws up, not just kids, but kids (especially at that age) keep making the same dumb mistakes. Remember, how many times did Ash try to use Charmeleon/Charizard before it started listening to him? Charmander evolved somewhere mid-Kanto, but it didn't respect him again until towards the end of the Orange Islands.
Why should they expect people to question the plot of a cartoon, especially from a group of teens and adults outside of the target audience?
That's why he starts over at the beginning of every region, to build more experience with new Pokemon, he just keeps Pikachu. When he went to Johto, he kept his Kanto team and his first battle had Charizard completely dominate the girl with a Rattata, Pidgey, and Chikorita. Do we really need to see more of this?
And the deal with Iris is a misunderstanding apparently thanks to the Pokedex.
Bulbapedia:"Ash walks into the forest, wondering what kind of Pokémon he will capture first. He then hears rustling from a bush he jogs past, and seeing something purple, he checks his Pokédex. The electronic gadget displays a picture of an Axew, apparently green in color. Talking about Axew's properties and behavior, Ash wonders why what he sees is so different from what it is being displayed. Nevertheless, without thinking, he throws a Poké Ball, and it hits... a girl's head! The girl rises from the bush, enraged at being thought of as a Pokémon. Apparently, it was actually her purple hair that Ash had spotted while she was picking fruits. Ash immediately apologies for his actions. Accepting his apology, the girl raises the fruit she had picked to her hair and an Axew pops out, grabs the fruit and lands on the ground, eating it."
Though it looked different, the Pokedex identified Iris' hair as an Axew, which it was right, but it was hidden in her hair. Not really Ash's fault that the girl hides her dragon in her big hair.
Snake is also an adult war vet, not a kid befriending magical creatures. Ash is a 10 year old kid, that's why he isn't all-powerful. He's obviously skilled, he's the only known trainer to ever KO Tobias's Darkrai, as it was said Tobias won all 8 of his badges with only Darkrai. No one had ever seen any of Tobias' other Pokemon before the battle with Ash. Ash was the 2nd strongest trainer of the Sinnoh league, as the guy who Tobias beat in the finals didn't beat Darkrai. Ash advances further with every league. Even if he were to perhaps win the Unova league, he may feel there is more to being a Pokemon master than just winning a tournament.
People act as if Ash is just a huge failure, yet as always, he wins his 8 badges. In Kanto, several of his badges were just given to him due to outside interference or something. At least in later seasons, he actually gets a clean victory when he earns his badges.
This was addressed on the Bulbagarden forums. Someone there said Japan's birthrate has gone down a lot recently, meaning there aren't as many kids to watch TV as there was in the past. And ratings for ALL the shows are going down, not just Pokemon's. People aren't watching TV anymore because 1: Not as many kids in Japan and 2: Why get up early to see something on TV when you can sleep longer and just watch it later online (though probably illegally)?
Except there is nothing suggesting Pokemon is in danger of being cancelled. It's still one of the top watched shows.
The Homika/Roxie 2-part was at 6.6 according to someone form Bulbagarden. Best Wishes tends to fall and rise frequently according to the ratings they posted there.
You would change a show, knowing the results would end it? That's horrible business logic and a total waist of money to produce something.
It's much easier to just say "our heroes" rather than name them individually every single time. They're reoccuring major roles, but Ash is the only true Lead role. The show is about his journey, not everyone elses'.
Again, he has skill, otherwise he wouldn't have all 8 badges of the 5 regions and the 4 from the Orange Islands.
Or, I think it'll be a good idea if, Ash travelled for its part, and we followed the adventures of another former character, like May or Misty. Well, maybe not Brock because we also had enough of him I guess.
Or, an anime with Red instead of Ash. An anime based on PokéSpe. We can dream, can't we?
There is no "must". They don't HAVE to change him. He isn't ruined, he progresses further every season.
Replacing him would only lead to another argument about the anime again in a few years.