This is an easy answer: not much. At least from Nintendo proper.
Nintendo does not historically attend Tokyo Game Show, instead opting to hold its own press conferences and private events. Usually, Nintendo holds an event that reveals a slate of upcoming games prior to Tokyo Game Show starting, but for whatever reason, that didn't happen this year. That doesn't mean we won't be playing DS and Wii games during Tokyo Game Show, however.
The interesting thing about Tokyo Game Show, however, is the surprises.
Looking over the list of games G4 expects to cover, there doesn't seem like much for Nintendo's two popular pieces of hardware, but unlike other trade shows, Tokyo Game Show has plenty of hidden gems. Many of these games we are completely unaware of until we are on the floor itself and discover them by accident or word-of-mouth from friends.
I'm actually most looking forward to checking out Capcom's Okami revival on the DS. Even though I haven't played Okami yet (a tragedy that I'm well aware of), there seems like a great opportunity for a franchise reboot on Nintendo's handheld.
Are there any games you'd like us to check out? Let us know!