A slight increase when production issues have been sorted out means little, but you're still ignoring that the Switch no longer has that launch boost which was nearly 3 million units, so Pokemon and Smash Bros have to somehow bring in an additional 6 million customers before you factor in the loss of sales from not having titles like Breath of the Wild and Splatoon in the early and mid year, the Switch is weighted almost entirely for the holiday season this year, where it will undoubtedly sell, but last year the Switch sort of had hitters year round.
Lets' Go was a flash in the pan, and it has no barrier to entry, it did cater to a different audience, but why would years after Pokemon Go hit it's peak would these same people suddenly jump on a Pokemon Game that only has in common with Go catching Pokemon game? I don't really see your point here. On top of this why would Pokemon Let's Go, a remake of older titles bring in the Pokemon Go audience with a buy in of $300 for the console and $60 for the game, and not Sun and Moon with $150 for the console and $40 for the game, this isn't a logical conclusion on your part. I never said that Nintendo fans are what selling Nintendo games and hardware, just that there was a significant overlap between current owners, Smash players and Pokemon players, and there is. These games didn't manage to push the 3ds to 16 million units over the holiday and post holiday season why would they do this on Switch with a far larger buy in?
No, third party support is poor at best. The Square Enix Switch department sounds at best like PR, there's already a Switch department at SE, it's called Asano team. Bamco talked about some new exclusives coming to the Switch a while back, turns out they are all being published by Nintendo, That can't be considered good support, it's not like Bamco are actually risking anything by making these games, to them it's just a paycheck. I never said that third parties weren't interested, I said that they weren't that interested, which holds, an overwhelming majority of A+ titles aren't coming to Switch, companies don't consider it as a platform most of the time, and in the rare case that they do come to Switch it's months to years later. The easiest way to sum up my claim is that Third party support is poor. I don't even have to add indies to the equation, because even with Indies Nintendo is still missing almost an entire sector of the market.
I think the worst part is that you seem to think that I think that the Switch will utterly stagnate, I just think that Nintendo's 20 million goal is a pipedream, it lacks the third party support that other platforms had to reach that goal in the sort of timeframe and 20 million isn't some small number, it's pretty significant.