Nintendo doesn't have a stellar track record of first party support once the new system launches
We already know a sequel to Pokemon Legends is coming out next year. Plus I expect the next mainline Pokemon game will still come out next Holiday as well for the Switch, similar to how Black and White came out for the DS after the 3DS was released. Yeah in Japan Black and White came out before the 3DS but even there Black and White 2 come out over 1.5 year after the 3DS was released. That was still a huge release for the original DS to have well after the 3DS . I still expect several more remasters and remakes to hit the Switch in the next 2 years, since they'll be a cheaper way to still sell games to the Switch massive user base. So I imagine the Switch post successor support will at least be similar to the DS and 3DS post successor lineup.
So if the DS could sell 7 million after its successor and the 3DS over 13 million, I don't see how the Switch doesn't at least do something between that range. Unless they just stop making units next year which I find hard to believe when they still made 13 million more 3DS after the Switch was released and the 3DS was performing way worse toward the end of its life then the Switch is right now.