This is a sentiment that I agree with, but I don't know why people are under the impression that Palworld is going to be the game that will do it. I'm speculating that once the initial craze for the game comes and goes, the player rate will die off hard, because it's game that seems to live and die on its premise alone. Games like Tem Tem also promised to provide a Pokémon alternative for jaded fans of the series (or non-Nintendo players in general), but it hasn't really done anything to threaten Gamefreak's bottom line, either.
But even if we assume that momentum for this game continues to grow, I don't suspect that the people who purchase Palworld won't buy the next Pokémon game as well. The overlap in demographic is 1:1. Scarlet and VIolet were critically thrashed on release and still went onto sell comparably to Sword and Shield, which also went on to be the highest selling games in the series since Gold and Silver, despite being marred in numerous controversies. Anecdotally, I know people who bought Scarlet and Violet despite knowing they would dislike it.
I just don't picture that Pokémon is going to change much in response to this. I think the next Pokémon game will release as it normally does and it will be business as usual.