Well, hmm... unless they want to do graphically-improved, differently-laid-out versions of the new tracks in Mario Kart DS (Delfino Plaza--why were all the trees orange?--,Tick Tock Clock, and so on), there hasn't really been too many significant Mario-related games lately (the aforementioned Mario Galaxy suggestion aside) to justify any "based on ____" levels. Obviously, there's original levels loosely based on characters's names to be made, but those are impossible to brainstorm, anyway.