So here's what the Wii Mario game will be like.
As far as level design ideology goes, it will share many elements with the "old school" levels of Sunshine. More linear progression is the keyword here, linear progression instead of open subworlds with several 'missions' in each. When it comes down to the actual shape and feel of the levels, obviously they will be shaped around the wiimote and entirely around the wiimote. Whatever funky moves Miyamoto has come up with will decide how the obstacles will be. Undoubtedly they'll open for great fun and never-before-seen platform dynamics.
Note I'm not saying it will "be like" the fludd-less levels in sunshine, just that it takes it's linearity and 3d-ness with it and develops it into something entirely unique. The look? Probably much more fleshed out than those levels of SMS I mentioned above. I'm thinking it will be a full-fledged mushroom kingdom-ish universe... basically envision the 2D marios and make them 3D, only more intricate (and yet again; not wide-open like SM64).
What will this give us: Linearity limits movement and enables miyamoto and his team to create a level experience tightly around the funky control methods... and enabling a game where - when players have become experienced - you'll be able to achieve that great flow, rushing through a level with precise and carefully planned moves, something half-way lost in the open-ended 3d universe of SM64 and SMS.
Anyway, that's my prediction and I feel it's a very likely path..
