Saw this link today of an interview with Miyamoto explaining a little bit on what they meant by "open world".
http://www.zeldainformer.com/news/miyamoto-explains-zelda-us-open-world-things-to-do-everyday#.U7WeE_ldUrY
Notice at the end he says they also have new ideas for the 3DS. Assuming that...
MM3D may be in the works after all.
I apologize if this has already been brought up, but I just saw this today browsing the internet (article is even dated today).
Definitely no confirmation, but seems promising :)...