Once again, the Best Wishes data broadcast system gives us some slight spoilers for upcoming, completely unrevealed episodes.
Episode 22's Pokemon doesn't really tell us anything beyond "Satoshi will most likely use Waruvial in a league battle this episode", but the Pokemon featured in episode 23 should be quite intriguing - it doesn't really seem like a Pokemon any of the known league rivals would have on their teams.
BWS2-22: Sawk Appears! Ash VS Stephan!!
Airdate: December 13, 2012
http://i45.*******.com/5zl55k.jpg (upper half)
The white-hot battles of the Unova League Higaki Tournament continue! Surprisingly, the opponent waiting in the third round is Stephan! He and Ash have fought in various tournaments in the past. Knowing each other's techniques, they take on the battle by predicting each other's Pokémon and moves!
Caption 1: Sawk easily blocks the attacks, as expected of the Karate Pokémon!
Caption 2: Stephan's Zebstrika knows a new move this time!