I think the general consensus is that Nintendo pretty much needs to show either a new Zelda or a new Mario for the Wii to satisfy us as gamers. Without one of those two behemoths, everything just seems small time.
The only other ways I could possibly see Nintendo's conference NOT falling on its face is if Nintendo announces new, non-spin off games for at least 5 of the following franchises: Metroid, Fire Emblem, F-Zero, Kirby, Star Fox, Mother, Mario Kart, Paper Mario, Golden Sun, Pikmin, Super Smash Bros, or Kid Icarus.
The last way I could see Nintendo redeeming themselves is if they pull out a HUGE 3rd party title out of their asses. Something akin to Final Fantasy Haeresis XIII or Grand Theft Auto for the Wii.