Ubisoft mentioned in some recent interview that Nintendo recommended they don't release Mario+Rabbids: Sparks of Hope on Switch, and hold it for the next version of console. It's better to release one game from each series on a console.
Which suggests that next 3D Mario, and Mario Kart would be on next console, but then they released two Xenoblade and two Zelda on one console, so don't know how strict they are about all this.
Thing is, you never know with Nintendo, we may call the direct "sunset slate", but we have 3 first party games in this year. Zelda, Pikmin and 2D Mario. Doesn't look like Nintendo is slowing down, but let's see.