I would consider the anime's depiction of Ash in Journeys and determine how willing are they to keep Ash as the lead AND the World Champion.
Because even a year ago, it became apparent that anime was going to make Ash vs Leon a thing, which placed Ash in an impossible situation.
Leon is the strongest trainer in the world, according to the anime. Cynthia just recently guest-starred in December 2021, and everyone knows her reputation as a formidable trainer. Naturally, we're going to need Cynthia in the World Tournament to showcase that Leon is indeed the strongest trainer in the world. But this would mean that if Ash gets to Leon in the World Tournament finals, he would have theoretically surpassed Cynthia, a feat that cannot be ignored. How could anyone believe that Ash would defeat Leon if he didn't defeat Cynthia?
Now, the anime could drag the world tournament for years or the Pokémon games could do something different for the typical Pokémon League. But when it became clear that Ash was narratively heading to Leon no matter what, and Leon's entire character arc is to be finally defeated (just like in the games), Ash becoming the World Champion was becoming more and more of a reality.
But Ash reaching at the top means something had to give way. I placed two scenarios before those skeptical of Ash retiring: Either the anime changes formula to accommodate Ash's new status as the world's strongest trainer... or Ash leaves. There can be no other path. You can't just have Ash lose to Leon because defeating Ash wouldn't help Leon become a better trainer. It just makes him stuck in an unchanging status quo that won't be revisited anytime soon. Ash has to win against Leon. He can't just lose to preserve the status quo. He's already breaking status quo with his new Pokémon and his new status as Alola Champion.
The writing was on the wall the moment they confirmed that Leon is the strongest trainer in the world, not just Galar, and Ash wants to beat him. If he had just been traveling the world with no clear goal in mind, then I would believe Ash stays forever. But since they gave him a goal in Journeys and its a status covers the entire world, suddenly I have to consider that maybe, just maybe this is the series where Ash and the audience part ways.