Since they don't consider any of the side games part of the main series my guess is they don't. With how stacked 8DX is in terms of content they're either gonna do that or make major changes that make it feel both fresh and a lot more advanced and it seemingly having 24 player races does add credence to the latter.

Plz no Nintendo Kart wishful bullshit. This is not a smart gimmick.
There's no problem a few select of those to supplement your roster but it cannot become THE feature everyone should look for.

Thankfully, it seems there using known quantities of characters from the series so far so I doubt the Nintendo Kart thing is even a thing, except for possible exceptions(Like the F-Zero tacks were)

MK8 had Zelda, Splatoon. F-Zero. Animal Crossing racers and tracks.

Not having 8 in the title will be truly innovative

I don't know, but I wouldn't be surprised if this was free to play MK ... additional tracks, modes, characters and karts hidden behind different/new tiers of NSO. The last Mario Kart, if you will.

Aim mechanics, like for example throwing a green shell, banana or a fire flower in any direction, not just in front or behind you and in addition to that, some melee weapon itens, that you could swing freely in any direction, like a baseball bat or a sword.

Also, I would love better physics, throwing the racer in the air when hited by a shell like in MK64.

Wonder seed could be pure chaos, it would be awesome if we also have elephant fruit as an item

Pit stop where you can hang around in a lobby (with friends) compare it to what Splatoon does.

I like the idea of world switching, since that could add things like big ledges to jump off, on a flat surface, etc.

Someone noticed what seems to be a fuel tank system though.

I thought this was the wonder flower in the trailer^^^

Mario Kart 8 Deluxe is still largely Mario characters and key IPs like Kirby, Pokemon, and Metroid are absent. Captain Falcon isn't even available as a character. 

Mario Kart is currently Nintendo's Top IP if we look at Mario Kart 8 Deluxe's sales and Mario Kart Tour. Heck, even Mario Kart 7 and Mario Kart 8 were the top-selling games on 3DS and Wii U. No Mario Kart title had been the best-selling title on a Nintendo platform until 7 and 8. Heavy emphasis on non-Mario characters and locations would be a huge gamble for the Mario Kart IP.