My bets are the following:
Sony:
-Ratchet PS4 will be shown off with a fall release date attached to it; Future Series + Into the Nexus Collection coming to PS4 with 1080p/60FPS, launches when the film does (July or August)
-Uncharted 4 Trailer and Demo; Fall Release date
-God of War PS4 announced; coming March 2016 and a HD Collection of God of War Saga + Assention coming Fall 2015 with 1080p/60FPS alongside a demo for God of War PS4
-Oshoka gets a fall release date, Killzone Mercenary ported to PS4 on PSN, Soul Sacrifice Delta ported to PS4 (...Sony hates the Vita, so why not
).
-Sony announces new Sonic tittle for 2016; based of upcoming film and it has gameplay similar to Modern Sonic's levels from Generations/Unleashed/Colors (they are making the film, so a little cross-promotion is reasonable
)
-Ico Collection announced for Vita
-Surprise PS1 IP gets revived for PS3/PS4/Vita (Ape Escape, Crash or Parappa the Rapper)
Nintendo:
-Zelda U gets a expansive demo, fall release date; Amibo support announced for the game (Link, Toon Link, Zelda, Shiek, and Gannondorf amibo have some purpose for the game; each grants Link tools for building weapons ala rewards Ambio's currently have for Hyrule Warriors
-Nintendo Announces Amibo centric tittle; all available Amibo works with the game and it is a hybrid of Skylanders and Mario 64; 3D platformer with each character having a unique skill (each character has an exclusive 'star' to collect while also having a level build around them ala Disney Infinity)
-SMT X FE comes back to life! The game is shown off being a successful hybrid of the two series and is on track for a 2016 relase
-Pikmin 4 is announced; summer 2015 tittle (August like Pikmin 3)
-Smash DLC is announced; works exactly how Mario Karts works. Three packs costing 8 bucks appeace with each pack having the following: Two characters, four stages (two retro stages, two new ones), 8 new songs (3-4 new, 4 old) and a wave of costumes for existing characters. First pack contains Mewtwo (for those who did not use the CN way of getting him) and Rayman (common, fake or not, it is the most likely third party rep after Snake or Simon Belmont).
-New 3DS gets two more exclusive games; Mario Sunshine 3D (fall 2015) and Zelda Twilight Princess 3D (2016). The former gets gameplay refinements based on Galaxy and 3D Land/World while the latter gets all the features OoT/MM3D had alongside refined visuals.
-Pokemon Z is announced; features from both X/Y and OR/AS are in the game
-Xenoblade X gets a fall release date for NA/EU (coming before Zelda)
-Star Fox shown off; mix between 64 and the two other demos Myamotto showed off last E3.
-Splatoon gets a season pass; explained at E3 if the game is out by then or latter if it comes out around E3. Works like Hyrule Warriors.
Microsoft:
-Sunset Overdrive sequel gets announced
-Ori gets shown off (if not out yet)
-Halo 5 shown off (Fall 2015)
-Tomb Raider 2 shown off (Fall 2015)
-Platnum X1 Tittle shown off (on stage demo); Spring 2016
-Rare does something! Battletoads coming August 2015 (HD Remake of the original made by the team behind the Banjo and Perfect Dark 360 ports) and Conker's Other Bad Fur Day announced (2016) with a on-stage demo of the games opening
-Crackdown X1 shown off
-Quantam Break shown off again; 2015 release date
-Indie games shown off; announce the end of stupid polices in place (meaning more indies can come to the platform)
-Price drop to 300 this fall; Halo and Tomb Raider bundles for 350