>>41009963Underperforming is very possible. Sure, it's reaching number one in Amazon rankings, but that's not exactly indicative of how much success it'll have. Only that it'll get lots of sales. When your franchise sells in the tens of millions, that ranking becomes irrelevant.
SWSH will not flop, but it might sell less compared to SM and XY. That might be enough to make Gamefreak notice and change their strategy. If not, it'll simply keep declining little by little with each release.