Ash will defeat Paul, that's something we all know. However, I hope that Paul doesn't change that much. As I see it, Ash will barely defeat Paul (either with Monferno/Infernape or Pikachu) and Paul will accept that Ash is a good trainer, and that he shouldn't have released Chimchar. Of course, Ash will give him the Soothe Bell. And this time, he'll keep it, to show that he's going to be slightly friendlier with his Pokémon.
Also, we have to understand Paul. He has shown respect to Cynthia, Brandon, Joy, and even Brock. He gave his Azumarill to a little kid instead of releasing it. And he doesn't hate his Pokémon, he just uses them to win. And all of his Pokémon seem to enjoy it, except for Chimchar. Torterra, Electabuzz, Ursaring... they all seem to like Paul's training method, because they're like him: they just want to be stronger. Ash is always telling Paul how he should train and how he should treat his Pokémon, even when Paul shows that he's stronger. Paul must be tired of Ash's speeches.
Paul is a good character because he seems to be the only character that wouldn't copy&paste that thing of treating your Pokémon like individuals instead of brainless drones. We need some different characters, and having someone who does what a competitive trainer should do is great.