I don't think the anime will end if he wins a league, but I just can't see him winning this one. For consistently (so far) strong Pokémon on a high level, he only has Leavanny and Krookodile. Pignite is strong, but isn't fast enough to hit fast Pokémon, and in fighting, speed beats everything if the speedster has even a modicum of skill and strength. Snivy is pretty good and can hit above her weight class and even win, but she is still a first stage Pokémon with not a lot of reliable status moves that could put her over the top against fully evolved Pokémon, even should she have the Contrary ability. As for the rest, Palpitoad and Boldore have not had that many good showings, and one lousy showing, with Unfeazant having a lousy showing with no other really outstanding showings to show that her power is reliable (after all, Skyla had used air battles for so long that her Pokémon may have been out of shape for their fights against Cilan and Ash). Still, Unfeazant would be above Palpitoad and Boldore in power. Now if Ash brings in some of his Oaked Pokémon, my opinion on his chances may change, but if he doesn't, I just can't see him winning the League with his Unova team only. Now I will say that this tournament's crop of competitors doesn't seem to be all that strong so that could give him a small shot, but if Virgil is shown to be strong in his episode, then I don't see Ash having a real chance at winning the Unova League.
Team Rocket will pay for their crimes.