This information comes from person, who works at Nintendo Europe in Germany and prepares few elements for upcoming show. Sorry for my English, it’s not my native language.
Nintendo Digital Event will be something between Nintendo Direct, and classic E3 stage show. This will be something like TV Show hosting by Nintendo executives (Iwata, Shibata, Reggie etc.) and with live audience (most of them will be Nintendo employees).
Nintendo knows, that upcoming E3 is the last moment for saving Wii U, so most of the time, they gonna tell about Wii U games, but of course there will be time for 3DS games too.
They gonna be two biggest stars of the show: new Zelda game, and Smash Bros (especially for Wii U).
New Zelda game – As they said, Nintendo will finally show us brand new Wii U Zelda. They gonna show us CGI trailer, and also a few minutes of gameplay. It will be true open world Zelda (Elder Scrolls style). It will have two regions, one dark and edgy. Second more colorful, just like Skyward Sword. Game will be playable at E3. Release date: 2015.
Smash Bros Wii U/3DS – They will reveal release dates for both versions (SB Wii U in November). Show more gameplay, and presents all fighters and stages. They will also talk about Smash DLC and NFC Figures.
Monolith Soft X (Xenoworld) – Open world jrpg with story mode and cooperation similar to Monster Hunter Games. You can play it alone with AI companions. Release date winter 2014 in Japan and march 2015 in the west.
Bayonetta 2 – Trailer and release date (fall 2014)
FExSMT/Yarn Yoshi – first trailers and release dates (first half of 2015)
Hyrule Warriors – first trailer, release date is October 2014. Hyrule Warriors is final title.
Fatal Frame/Project Zero – first CGI trailer, “coming soon”
Retro Studios Game – New IP, sci-fi action adventure game, first CGI trailer, “coming soon”
New Miyamoto’s game – Lots of Gamepad and NFC gimmicks.
Mario Party U – Nintendo’s holiday game for casual gamers, classic Mario Party, but with NFC figurines.
Pokken – first trailer, Pokemon fighting game from Namco, 2015
Smash Bros – more details about 3DS version
Pokemon Omega Ruby/Apha Saphire – trailer, details about game
Tomodachi Life – trailer, details
Yokai Watch/Dragon Quest VII – west release announcement, trailers, details and release dates (autumn-winter 2014)
Metroid 3DS – developed by Next Level Games, classic 2.5D Metroid, trailer, release date: December 2014
BIG FINAL SUPRISE
Star Fox – reboot of the series, developed by Platinum Games. First trailer, CGI and gameplay. Game is mix of Star Fox Adventures and classic Star Fox games. Release date: 2015.