Well considering the length and the number of know Wii U titles coming up, there isn't much room for a SUPER SURPRISE. They have live 10 Wii U games to show and we know about all of those except for Retro's game.
I also have a feeling they'll announce cross platform Virtual Console games, along with a more uniform account system. They have already mentioned bringing the handheld and console teams closer together, and them announcing Wii U GBA VC support but not 3DS GBA VC support (despite having a decent GBA emulator working on the 3DS already) makes little sense. Even by Nintendo standards. That, along with promised Miiverse for 3DS gives me a good feeling about the future of accounts on Wii U and 3DS.
Other than that, I expect the usual stuff they've mentioned already. The Galaxy Mario silhouette makes me worried that it'll just be Galaxy 3, though. Galaxy 2 might be the greatest platformer ever made, but I want Nintendo to shake it up about like they usually do with 3D Mario, rather than NSMBifying it.