I will go from publisher order like you did OP to keep my thoughts organized
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Bethesda: More information on Doom alongside some post launch support announced for the title. I also expect Elder Scrolls Next-Gen to be announced for PS4/X1/PC alongside a live demo of Dishonored 2.
Sega: Sonic Anniversary to be announced at one of the press events (Sony, MS, Nintendo) alongside localization news of a few games (Project Diva X, Valkyrie Chronicles PS4 Spiritual Successor.....maybe PSO2 (not holding my breath on that one)).
Nintendo: All-out information dump for the NX, announced here. Information on the system, launch line up, and a few game announcements/partnerships with 3rd party detailed. Expect 3D Mario, Retro's New Game and a New IP to be announced alongside Zelda U and Pikmin 4 to be officially announced/detailed (official name, release dates, cross-gen, ect). NX system and handheld shown off to press with playable kits on the show floor.
Bandai-Namco: Digimon New World Order and Summon Night 6 announced for localization alongside solid release dates for a number of games (SAO Hollow Realization and God Eater come to mind). More news on Tekken, Ace Combat and officially unveiling Tekken X SF as a PS4/X1/NX/PC game.
Square Enix: Shows off a lot; more gameplay of FFVII Remake during own Press Event, FFXV shown off (if its not out yet), and Nier 2 shown off more. Other stuff will be announced/shown off but I expect that happening for Sony's event.
Konami: #FuckKonami
Activision: TMNT shown off (if not out yet) with another Platinum game announced (Spider-Man? Transformers Devastation 2?) at Sony's event alongside Call of Duty IW. Skylanders Six shown off during Nintendo's Event with Amiibo Support continued (Mario, Kirby, and Link added to the new game, alongside DK and Bowser Skylanders supported).
EA: Battlefront Season Pass shown off during Sony event, Titanfall 2 shown off during Microsoft's event (though Multiplatform), and Mirrors Edge shown off during Sony's event. New IP (ala Unraveled) announced.
Sony: God of War IV, Crash Bandicoot Returns and Sony Bend's New IP announced alongside showing off stuff from first (Ratchet, Uncharted, GT Sport, Horizon, Dreams, PS VR, ect) and third party (EA, Activision, Square Enix, Bandai-Namco, ect). Major third party content includes information on FFVII Remake & KH3 (New World(s) shown off; Frozen and Star Wars).
Microsoft: Support with Window's 10 detailed more with apps officially being added into the X1 OS, sequel to Sunset Overdrive announced/New IP with Insomniac announced, stuff announced detailed (Halo Wars, ect) and more new games announced.
Other: Indie projects like Shantae, Mighty No. 9, Bloodstained, Yooka-Laylee, Bikes & Knights, and more shown off with great detail (taking advantage of the E3 hype/attention).