Now, this is obviously just my opinion. I don't expect everyone to agree with it, but we can still be friends and agree to disagree.
Win or lose, this battle is now going to negatively effect the Anime moving forward.
If Ash wins, it is going to have to be some type of plot armor. The only realistic way he can win this is by gaining an extra G-Max for Pikachu. Pikachu has to defeat a completely fresh Charizard and a hardly damaged Cinderace that he is ineffective against. That means in order to beat Leon, he needed to use 2 G-Max, 1 Z Move, and 1 Mega evolution. That just doesn't make this a clean win in my opinion.
If Ash loses, you either replace him or have him go to the next region where the only thing left for him is to eventually rematch Leon. That doesn't need to be an entire anime series.
Here is what I would like to happen (again my opinion). Ash should lose to Leon with the current scenario (They definitely could of/should of had dracovish and sirfetch'd defeat or nearly defeat cinderace). It will be a really close battle and Leon will welcome Ash to a rematch. There are still episodes left in this series, so Ash should rematch and defeat Leon using Pikachu and his reserves. Ash becomes the top battler and they can move on to a new story.
Actually even if both Ash and Leon didn’t get a 2nd Dynamax Charge so that can Gigantamax for a 2nd time Ash and Pikachu could still beat both Leon’s Charizard and his Cinderace as it doesn’t look Pikachu is in that bad of shape and the remaining part of its battle with Charizard will probably just ge in their base stage.
Now as to how Pikachu can beat Cinderace that can change its type it’s actually not that hard considering Ash and Pikachu now know what they are up against.
For instance Pikachu can use its speed to dodge Scorching Sand and hit Cinderace with a Iron Tail and/or Quick Attack and then when Cinderace eventually hits Pikachu with Iron Head it could trigger Pikachu’s ability static Paralyzing it.
After this as the battle goes on Cinderace could try to use High Jump Kick on Pikachu but Pikachu dodges which causes Cinderace to take damage and then Pikachu follows up with a Thunderbolt.
Cinderce tries to counter this by using Scorching Sands to switch to a Ground type but it’s paralysis stop it from being able to do so causing it to be hit by Thunderbolt and take damage.
I mean heck when you really look at it Cinderace is very likely a glass cannon in that although it is extremely strong and fast it doesn’t have good defense.
As for Leon’s Charizard since it’s pretty much stuck in its base form and as Pikachu likely has gotten a lot stronger since the last time they fought, although Charizard will likely be able to put up a fight Pikachu could be able to beat it.
Really the only reason why Pikachu is going to Gigantamax here is to counter G-Max Cinderace.