[Kegan]
Just have ash meet up with and pokemon battle his father and end the series on that. Brock and misty can show up, or maybe they'll see ash on TV and sigh longingly.
We all have fanfictionish dreams of what the last episode of Pokemon would be like, and I'd like them to at least mention his father another time. I think they only do what, once?
Though as a child of a single mother, I think it helped me bond more with Ash. Still, it's the biggest mystery of the show outside of Ash's relationships with the myriad of women he travels with and they shy away from both now in order to keep the show going. I hope the finale, whenever they decide to end the show, is a movie involving his father.
I really wish the characters had aged at least a little (rather than the reverse-aging they're doing now) and that Ash could have passed the torch onto someone else or something. What was that one series called with Gold and his Typhlosion? I think I remember seeing a few episodes on Toonami. It wasn't bad and it would be an awesome way to keep the series going, enticing new, young fans, while letting older fans watch with the children of today.
I don't see Ash really as the professor type-at last not like Oak, but it would be neat to see him as a mentor of some sort, older and more matured from his decade+ of traveling and training.