Yeah honestly if it wasn't for the fact that I think Nintendo wouldn't go for 3 Mario games per year I'd agree.

Actually you could probably Switch BOTW2 with Mario Odyssey 2 on my list and just erase Mario Golf altogether, who knows.

Mario's not just one series though. There's multiple Mario-related games released each year in one of various series. Hell, this year alone has NSMBU DX, Mario & Luigi Bowser's Inside Story, Yoshi's Crafted World, Super Mario Maker 2, and Luigi's Mansion 3. All star Mario characters, but are vastly different from eachother in terms of series. I don't see why 2020 will be any different?

I'm still not convinced Mario Kart 8 Deluxe will be the only Mario Kart on the system. If Mario Kart 9 is ever gonna happen, it's gotta at least be shown next year.

Yeah, I'm beginning to doubt that more and more as time goes on. MK8 DX is STILL making Nintendo so much money, and Mario Kart is typically one-per-system like most of Nintendo's other series. It's the best selling game on the Switch, so why negate that with a new Mario Kart? I think ARMS 2 is far more likely to come first before MK9, which probably won't happen till the next Nintendo console at this point.

Pokemon lets go pichu/togepi, remaking HGSS, including until gen 4 pokemon, and alolan, galarian forms, and megas
pikmin 4
Zelda GC collection: WW & TP HD + four swords for joycon .
new paper mario
Mario party n+1

It is one per system but that was when they had to make Mario Karts for both console and handheld. They were also brand new games each time rather than an enhanced port. A new game on Switch wouldn't negate MK8D, sure it'll undoubtedly take some sales away, but having two 15m sellers is better than one 20m seller for example. If MK9 skips the Switch, I think the reason would be that they don't think they can outright top MK8D, that it wouldn't be different enough without better hardware for noticeably better graphics.

I just think with MK8 DX, the team feels like they're set for the Switch at the moment. Unless you were one of the 3 people owned a Wii U, MK8 Deluxe might as well be a new Mario Kart to most people, so I think Nintendo is in no rush to have a new one out yet. I feel like the team will be focusing more on both Mario Kart Tour and ARMS in the future. ARMS especially since there's still plenty of room to build on with that series, and I think a sequel is coming much sooner than some people expect.

You're making a huge stretch by saying "Mario related". Don't play naive. Yoshi and Luigi's Mansion are basically their own franchises. A port to try to put steam in a dying system hardly counts, especially when it's the last release for Nintendo's old 2-console model. 

I'm not saying we can't have multiple Mario games per year, there's actually consistently been two Mario branded games a year for Switch since 2017. I'm also not saying it's never happened. I'm just saying 3 brand new Mario-centric titles in a single year for a single system is probably a bit much honestly, especially because Nintendo more so than with their home consoles are going to have to figure out how to stretch Switch's appeal for as long as possible. At that point just extend some of that Mario appeal to another year or something. This is all on one console, not two. 

They're still Mario characters, they're still set in the Mario universe. They're still tied to the Mario brand. So both Yoshi and Luigi's Mansion still count.

Even still, Nintendo will want to make sure there's enough Mario-related content on the system every year, especially to help keep software and hardware sales up. Like it or not, Mario as a brand sells, so there should be a good 3-4 games staring a Mario-themed games each year, in addition to other non-Mario stuff as well. There is such a thing as too much I agree, but nobody will complain about a handful of Mario Character games every year, especially if the games are at least decent.

Hm no I really dont think they will make another MK for switch when you see that it is still top 3 best selling games for switch WW each month years after its release. I think they could try and push a new racing game instead. Like where did the SF racing game from retro go?