I think that what Nintendo did in 2006 will be more indicative of how E3 2009 will go than any other year. Pulling out all the stops.
Why?
Look at the situation they were in then, they needed to really push the system hard and I think that with the economy the way it is, they have to do that again.
They have to show that the console is really coming into it's own now and that from june '09 to june '10, the support will only get bigger and better.
I think that Pikmin 3 may be their mass market traditional game or perhaps border closer to that than a bridge game.
If Kid Icarus is returning on Wii then I think this will be the year to show it.
Zelda doesn't have to be shown to make it a big show but a trailer would certainly help.
Nintendo said at E3 '08 that they were working on their idea of social networking so we may see that come to fruitation
They also spoke about expanding the horizons of the DS with other functionality such as the airport stuff, perhaps we may see some of that.
Ok i'm rambling so I'll condense my thoughts a little..
1. Wii Motion Plus - They'll show games such as Red Steel 2 and their own that use it
2. Third Parties - On Wii and DS, third party games will be showcased
3. DSi - They'll show new games that use the specific functionality of the DSi
4. Sales. The boring graphs will be there :P
