Originally Posted by DiZ
I know he is growing, because, the last time we heard of his age, he was 11. Remember in the 3rd Pokemon movie short, when Pikachu met the Pichu brothers? Ash, Brock, and Misty celebrated the day Ash and Pikachu met, which was Ash's tenth brithday, so, when that party took place, he was 11. I'd say, once the new Pokemon movie, Pokemon Ranger and the Temple of the Sea comes out, he'll be about 13 years of age. You can guess how I came to that conclusion
While that may be true, don't expect to see any physical change to ever happen. It's just that Pokemon is a continous ongoing story, but that doesn't mean that in ten years, we can expect Ash and everyone else to have totally different appearances (In terms of psysical goes).
And that's already true with Pokemon being more than 10 years old.