There would also be many people who would absolutely buy the game on the next system if Nintendo had released it exclusively for that and utilizing it's power that won't buy it on Switch 1 because of redundancies. So then the question becomes which one gets them more money in the long run:

A) Release a second Kart on Switch. Get some portion of the overall MK8 crowd to buy it, some new people altogether to buy it, but then sabotage MK8D sales going forward due to cannibalism and make the demand for MK10 fall down for years because many MK fans will have already been recently satisfied.

B) Release 9 on their next device. Lose out on a couple years of potential Switch 1 customers by making it a Switch 2 exclusive (though the final two years of a console aren't as lucrative as the first 4-5 anyway as sales always fall off). But then MK8D will keep selling (at no extra work for Nintendo) and the demand for 9 on Switch 2 will be so high that it sells like crazy when released.

"MK8 is easily the best kart game to date". With such bad item balance, hell no.

"it will take time to develop something better."

How much time do you believe they need? This is the seventh year since Mario Kart 8 first released. Are you people even counting? They should have enough time to release a new Mario Kart this year, and then still have another one cooking to be released for the next Switch by year 3 or even year 2, as the Switch still has crazy momentum and won't need replacing any time soon. Mario Kart 9 on switch is the most logical course of action to ensure that momentum keeps rolling.

They haven't released a single new DLC pack or track for the game since early 2015. I played hundreds of hours on WiiU, and even though I always plan to buy it again for Switch, part of the reason I put it off is I still have mental fatigue from the time I sunk in. Even Switch only owners will be reaching that point sooner than later.

Why would you want to blue-ball that huge player base while missing out on massive guaranteed sales, along with a big late-life boost for the Switch, just to put it off several more years for a system we know nothing about?

Because MK9 will have massive hype on Switch 2 launch leading to crazy sales, which will then lead to better sales for all their games. 3DS bombed hard in its first 7ish months on the market until a price cut and MK7 came out. Wii U bombed in part because MK8 didn't come out until a couple years after Wii U released. Switch sold like crazy because it had MK8D right at launch window.

If they release 9 now, I firmly believe 10 won't be ready until 1-3 years after Switch 2 comes out, which would not only sabatage their new system's hardware sales but also all the other game's sales. Mario kart is the bandwagon a lot other games thrive off of ever since the Wii game. I don't think it's worth it to them to release 9 now (which would sell great, but will diminish sales of 8D significantly), and lose all the money from a mediocre Switch 2 launch without a game.

And I don't think releasing 9 on Switch and Switch 2 will work like it did with 8/8Delux because so many more people have bought a Switch and will be familiar with 9 on it that they won't be as interested in getting it on Switch 2, further hurting sales. Nintendo is focused on the long te profits across all their games and hardware and not focused on the profits that one game could produce right now.

Mario Kart 9 at launch with a Switch 2.... that would be the smart move.

I don’t see why Nintendo would release MK9 yet. Mario Kart 8 Deluxe is still selling well and new instalments only really come along with a new console. They aren’t really in a position that calls for them to break the cycle.

They’ve been predicting it for years now, eventually they’ll be right and then they’ll pretend they are prophets =D

There really is no need for a new MK on Switch. I hope they are saving it for the Switch successor and hopefully it launches day 1. The Switch successor would be an instant success! If they released a new one on Switch, I can only imagine it would make things harder for the successor.

That being said, I wouldn't mind a small amount of DLC for MK8 DX. Maybe we will get something for MK 8DX next year for the 30th anniversary of the series. I wouldn't expect nor want anything major, but another row of characters (mix of returning and new), along with 2-4 more cups (again, mix of returning and new) would be nice.