I see a lot of people pissed about Ash losing in Pokemon. I'm like 15 years behind in the show but from what I understand Ash never wins a tourney and the show blueballs their fans. I watch some sports anime and that would suck if I invested so much time just to see the MC lose for over a decade. I remember the end of Haikyu 1st season left me mad as hell, but season 2 made up for that.
And who's Ash hanging around with now? What's up with Brock, Misty & Team Rocket? Is Ash's mom still secretly banging Mr. Mime?
The thing is that this season had a lot of development towards Ash finally winning a League. His team (Pikachu, Hawlucha, Greninja (with Mega Evolution), Goodra, Noivern, and Talonflame) was arguably his strongest yet. He managed to defeat the Trainer that would have normally been his downfall in previous seasons. He was able to go toe-to-toe with a League Champion and do actual damage for the first time ever. He took out multiple Legendaries using only one or two Pokemon each. He challenged Alan (the guy he lost to) twice and got better against him each time. Then the actual match comes. Noivern and Goodra go down without taking out a single Pokemon, but Pikachu took out both a Tyranitar and a Metagross by himself.
Then, it came down to Ash-Greninja vs Mega Charizard X. Charizard had gotten hit by Pikachu's Thunderbolt earlier (before Mega Evolving, mind you), took a Cut, several Aerial Aces, a Water Shuriken, and a Super Water Shuriken that was stronger than anything Ash has ever used before, and Charizard looked no worse for wear. Meanwhile, Greninja took two Dragon Claws and a Blast Burn and fainted. Keep in mind in the last match he took several Leaf Storms and Frenzy Plants and was minimally damaged.
It's not quite as BS as the losses in Sinnoh (Trainer full of Legendaries) or Unova (Idiot Trainer has a Hydreigon), but because everything in the story has been leading to Ash getting over the hump (unlike previous regions where Ash suffered a big loss or two beforehand or he had a very underdeveloped team), it really, really felt like this would be the year. And that has pissed a LOT of people off.
As for the traveling companions, Misty left at the end of Johto to go back and become a Gym Leader, mainly to bring in a new female character (RSE playable character May) to boost ratings, though Misty herself stopped being an actual character halfway through Johto. Brock stayed on through the end of Sinnoh, where he returned home to help his brother be a Gym Leader and learn to be a Pokemon Doctor. He was even more superflurous than Misty since all he did through Sinnoh was get jabbed by Croagunk and call out Happiny to move things. His last capture, Happiny, happened 1/4 of the way through the saga.
Currently Ash is traveling with Serena, the PC of X/Y, who is the first real legitimate companion that wants to be Ash's girlfriend, Clemont, the Lumiose City Gym Leader who is an inventor, and Bonnie, Clemont's sister and keeper of Zygarde-1 (nicknamed Squishy).
Team Rocket's still around, though they get pushed to the sidelines a lot more often and likely will moreso now since Lysandre has started his invasion and attack of Lumiose City.
If Ash wins, they'd have to move on from him as the main character, wouldn't they? I mean they seemingly had the perfect opportunity to do so with XY and didn't, so Ash and Pikachu will be around as the protagonists forever, resetting their Pokemon every few years.
What happened to all of Ash's old Pokemon, anyway? Does he just give up on them when the shiny new ones come along?
No, they wouldn't have to move on. Ash is not somebody who can rest of his laurels, otherwise he would have retired after winning the Orange Islands or accepted Brandon's offer to be a Frontier Brain.
Starting with Hoenn, Ash leaves all his old Pokemon with Professor Oak, though likely Goodra will go back home to its marshland. Charizard is also back at Oak's, as it came back for good at the end of Unova. The sole exception is Aipom, who was caught at the end of Battle Frontier but stayed through Sinnoh since Diamond and Pearl introduced a new Evolution for it.