It's looking more likely that Peach's Castle is going to be at ground level and that you will have to go "upstairs" to ride MK. I actually thinks this makes more sense from a design perspective as 1) There's less space to work with so you have to only put in what you need. Not really any reason to add a stairway that goes into the ground when creating more stairs requires space and the secondary ride that enters down there has been eliminated. 2) When you enter, you can see everything above you making it a more powerful "grand reveal."