In a recent interview with El Mundo, a Spanish newspaper, Miyamoto mentioned that Mario for the Wii-U would be shown off at E3. Whether this was a new Super Mario Galaxy game or "Super Mario 4" is unknown. Recently a domain for Super Mario 4 was made but no other news about the domain or the game have been revealed as of yet.
Besides Mario, Miyamoto mentioned that he would be working on other titles such as Pikmin 3 for the Wii-U and Luigi's Mansion 2 for the 3DS. Both titles I'm sure you guys are waiting to take a crack at. Miyamoto did not mention in his interview with El Mundo whether or not the titles would be available to play at E3.
On a more odd, or not so odd, note; Miyamoto apparently was in the process of making a music title for the Wii. Wii music is what it would have been called had the music simulator met its expectations. However it appears that Miyamoto is not giving up and will "do more" with the idea. It just goes to show you that even the great Shigeru Miyamoto makes a flop once in awhile.
Source: Nintendo Universe