The gif with the triple jump looks like a Mexican themed hub. I could see a "Super Mario World" with ethnic touches on various worlds besides the trite lava, snow, grass, etc ones.
Also the fact that the Switch joypads are analog only could signal that an isometric 3D Mario a la the Wii U one is off the table imho. We should get full 3d analog movement again.
Now, the multiplayer is REALLY interesting as co op in a SM64 style platformer would be amazing (actually there is SM64 romhack that does just that and it is seriously fun to play with a friend). I would like to see it not being restricted in mini games or modes but the full game.
That's the one amazing thing with the Switch actually. Virtually, any game, like this one, could have LAN multi with different consoles. They should use that a lot, maybe create mini games like in mario 64 ds.