In a video interview with Zoomin Games, Shigeru Miyamoto is revealed to be working on an "undisclosed original title" on top of his other projects, which include Pikmin 3 and Luigi's Mansion 2.
The manager of Nintendo's EAD division also talks about being jealous of his character creations outliving him and how he prefers to work on different looking games, rather than photo-realistic ones.
See the video interview below.