In an interview with Nintendo Power, Eiji Aonuma said:
It’s been 13 years since Ocarina of Time was originally released, and one of the big things that we made this remake possible was that there was an outpour of emotions from people who said they would like to see this game done. We said we could do it in 3D, so we did. I think certainly if there was a similar output of emotion and clamor from fans for a remake of Majora’s Mask, it wouldn’t be an utter impossibility.
Essentially, Eiji stated there has been such an out cry for an Ocarina of Time remake that it was the leading factor in deciding it’s creation and would again be the main factor in Majora’s Mask 3D becoming a reality. Hence, Operation Moonfall, an attempt to show Nintendo loud and clear the desire for Majora’s Mask on the 3DS.
It should be noted that Operation Moonfall in no way is here to encourage Nintendo to slow down the creation of a brand new Zelda title for the 3DS, but rather to encourage the creation of Majora’s Mask 3D along side of the new project to fill the gap between releases