Sony is better about keeping momentum than Nintendo. Sony puts a few big blockbuster games on their console leading up to the release of their new one. Nintendo generally lets its systems quietly just die. You might get a cross-gen game but not always. Switch sales are peak momentum now and while Switch will hit 100M. PS4 will just sell more since Switch is likley peak now and in 2022 leading into maybe 2023 new releases will slow to a crawl from Nintendo.
Oh no doubt (at least with hardware, as Nintendo 1st party software often just sells for the life of the system), but that doesn't mean Switch has no momentum, the sales will not hit a wall even if Nintendo stops supporting it with games.