Not an expert on the matter but Aonuma getting a lot of suggestions from fans in his public viewings as well as talking a bit about Majora in some interviews.
ANd Robin William's daughter appearing with Majora's Mask at the Smash Tournament.
- Happy mask man has his Majoras Mask backpack in OOT 3D
- Majora's Mask soundtrack CD was a club nintendo reward, seemingly at randon
- Bill Trinen showcased a majoras mask item in animal crossing during a direct
- Majoras Mask prominently shown in the most visited location in LBW
- Grezzo job listing "help us make a legend"
- References to the MM3D petition made by nintendo, they said it would be a possibility
- When asked about Majoras Mask 3D, Miyamoto stated they wanted to do an original 3DS Zelda before releasing another remake.
- Skull Kid assist trophy shown off prominently during Smash Bros promo material
- Satoru Shibata smiling and saying "please wait" when asked about Majoras Mask 3D a month ago