I I don't think they will make a new one, they will probably port mk8dx and use the same online servers so old switch users can play with switch 2 users.
For Mario kart 10 since Nintendo said tour was the 9th game and instead of Mario kart 10 it could be Ultra mario kart where it’s a bunch of different maps and you could have styles like double dash for it classic with Mario kart 64 or the og one or mario kart Wii and each style would have each map kinda like it except for some maps that are too complex but would be really cool