Well they've already said part of what'll be there, and the fact that Wii U got very little attention in this Direct episode just further signals that they're keeping most Wii U announcements secret until E3.
So far, we know:
3D Mario in playable form
Mario Kart Wii U in playable form
Wind Waker HD
X
Smash Bros reveal for 3DS/ Wii U
Yarn Yoshi
Shin Megami Tensei x Fire Emblem