Although infendo has been a rather trustworthy site over the years it's really hard to think Nintendo would do this. I know they need a way to strike back but I doubt having an early Zelda trailer would do that. Not to mention first trailer release at that media conference would just seem weird. For one of the biggest series in the world... you unveil at the E3 conference.
However, a zelda project was shown off at Spaceworld 2000 (essentially what Nintendo's October media briefing is) so I guess it's not so unlikely.
Really I would think the media conference will be there to further hype Wii Fit Plus and New Super Mario Bros Wii while giving some new media attention to Sin and Punishment 2, Endless Ocean 2, and other titles they have going. If any big game announcement is going to come out of it, it'll probably be Pikmin 3 announcement along with trailers for Galaxy 2 and Metroid: Other M. But considering it's a media conference we might see new colors and a potential price drop as well.
But expect something like last year... lots of games shown off with a few big announcements. Don't expect the megaton though haha.
