how is it confirmed that he will beat sawyer
we only know they battle in the semifinals
While I'm not even going to start guessing where this all leads (though doubt Ash will win the League, I'll go for
Norne's theory of Ash facing & beating Sawyer in the semi-finals followed by losing to Alain in the finals), it does bring up a question about how this league is set up. We know early in the league that Sawyer and Alain face each other so it seems like if you lose in the preliminaries you're not out. Now in Johto/Silver Conference they had something similar where one round was a best 2 out of 3. Could be the same thing here for preliminaries?
Though this is looking to come out better than Unova's Pokemon League, though that isn't saying much as Ash beats his main rival in a 1-vs-1 preliminary, loses to a incompetent character with a god mode Lucario in the semi-finals (who Ash met just before the League and had to help multiple times to even be able to participate in the League), and said incompetent character loses to another more interesting character in the finals (so they might as well has Ash just face that trainer, it would have also been nice setup for Gen VI as said trainer, Virgil, had an Eeveelution team (with a female Eevee that didn't know what it wanted to evolve into... and a month after the Japanese episode airing they revealed Sylveon)). I also think it was the shortest League getting only 5 episodes, one being filler where Axew gets lose, and they skip most of the battles except it was between two important characters. Only interesting battle was between Ash & Stephan.
Honestly I think the best league was Sinnoh (Johto a close second). A lot of battles, awesome rival battle, and even though Ash lose to a trainer who using Legendaries let's not overlook the fact Ash beat two Legendary Pokemon whereas the rest of the League couldn't beat Tobias's Darkrai. Plus Ash called on his reserves which he should do so for every Pokemon League, it's nice to see him use his team for that region for Gym Battles and during the League but no trainer in the League is holding back so Ash needs to bring his A-game and any Pokemon he has available to him (and don't say he didn't have access to his reserves, they could have BSed a reason like the teleporting machines at the Unova League are strong enough for far away region Poke Ball teleportation or just have Juniper act as a middle person between Ash & Oak).
Course doesn't look like we're going to see the reserves again (otherwise Ash would be the one with Mega Charizard Y) and with Sun & Moon coming out the League might also be short, though in the trailer we did see Ash at least battling other trainers.