But at a certain point we're going to get diminishing returns. People who might buy MK9 probably already bought a Switch for MK8, people who might buy Splatoon 3 already bought a Switch for Splatoon 2, people who might buy Zelda BotW 2 already bought a Switch for BotW, and so on. They will move hardware, sure, but there's a long road to 150m units, and I'm not sure if this will be enough to get there. Games like Pikmin, Metroid, Bayonetta... will sell well, but they aren't traditional system sellers.
And as for 3rd party, most of them are going to focus more on the PS5/XBoxX. They've had four years to bring big titles to the Switch, and yet there haven't been that many big projects coming. Monster Hunter was obvious because it sells the best on handhelds and the Switch is the only non-mobile handheld around, but other than that? Either PS360 ports (and even then you'd think we would've gotten way more of those), general multiplats like Minecraft, Just Dance, Fifa... or relatively small projects like Octopath Traveller. It would be weird for them to now of all times focus on the Switch, when the new consoles are starving for content. It's unlikely that any 3rd party project will become a major system seller, especially now that the userbase is already above +80m.
I mostly agree with you. But there are some points:
- "People who wanted to buy X game probably already have the console" never been a real thing, cause system sellers always push hardware, despite the age of the console. God Of War did, despite launching almost 5 years after the launch of the console, Red Dead Redemption 2 did, Final Fantasy 7 Remake did (despite being released the "last year" of the console), Ghost of Tsushima and Last Of Us Part II did as well.
- People who weren't old enough to have a console back in 2017 when Splatoon 2 was released will eventually be old enough to enjoy Splatoon 3 in 2022. And I personnaly lived this, I was born in 1992, got an original Game Boy in 2000 with Pokémon Blue despite the console being released in 1989. And we'll have kids, who weren't born yet when the NX was announced, that will be old enough to enjoy Pokémon Legends (or Diamond/Pearl remake) now.
- Regarding 3rd parties, as I do believe as you do that no real 3rd party will boost the sales of the console (with exceptions), the great 3rd party support (which is still growing, and become very impressive) definitly help the console sales. I still hope that GTA V will eventually come to the system, with the PS5/Xbox versions.