Confirmed in the movie, kind of. Meowth Stated that they had been after Pikachu from before Dawn was born, hence Dawn is 10. Therefore, They admitted they've been doing it for 10 years. Therefore, Ash is 20. (they knew she was 10, because she was a beginning trainer.)[/QUOTE
"We have been in pika persuits since you've been alive"
this staement doesn't actually refer to the amount of years team rocket in the anime timeline has been chasing pikachu. what it does describe is how long the show has been going on. the show started in japan April 1 1997.
and as for ashes age I really dont know. Mainly because his physical appearance hasn't changed at all if you dont count his clothes which are the same size as his original clothes. he has gained more experience, that is true.
I am curious are the pikachu shorts part of the series?
if they are not then ash is still 10. because there hasn't and correct me if I am wrong been an anniversery in the actual movie or series.