Traditionally the E3 expo is when and where all the big games, projects ahd hardware for all major games/media companies are unveiled. Last year Nintendo broke the rules (oh no!) by revealing a few of their 3rd party titles before the big trade show.
According to Nintendo Dream, a well respected Japanese magazine, Nintendo is planning to do the same thing this year, but the titles they will show are currently unknown.
Last year Nintendo chose to have Namco and Sega show off their games before the show, however there is no word on what titles may be shown or if in fact it will be third parties again this year.
[ Source: GamerFeed. ]