Nintendo:
Nintendo has a Pre-E3 direct and and talks about what they will be showing.
Nintendo makes a return to stage presentations at E3 2016 and reveals NX home console and portable.
Nintendo NX home console is more powerful than PS4, costs $400, also has some sort of 4K Capability similar to the PS4K, and will be available holiday 2016. (This one is more of a hope rather than a prediction since this is Nintendo we're talking about and with all the NX "rumors" anything can happen).
Zelda Wii U is also a NX launch title similar to Twilight Princess, game looks amazing on Wii U but the NX version blows it out of the water.
Pikmin 4 is a NX launch title and a new 3D Mario is available either at launch or launch window.
Retro Studio's new game is revealed for NX.
Beyond Good and Evil 2 rumor is true and the game is NX exclusive at launch.
Smash 4, Splatoon, Super Mario Maker are receiving NX ports as 'definitive editions".
Nintendo talks about how they have taken third parties more seriously and show a video of all the third parties and games they are bringing to NX. (Once again more of a hope rather than prediction, please Nintendo).
Microsoft:
Microsoft talks more about Windows 10 and Xbox One connectivity.
Recore, Sea of Thieves, and Crackdown 3 all get gameplay demos.
Microsoft promotes Scalebound a lot, game looks incredible. New trailer and gameplay are shown.
Phantom Dust is revealed to still be alive and will be launching in 2017.
New Battletoads game is revealed, being developed by a smaller team inside of Rare, releasing in 2016.
Teaser for Halo 6 is shown. Also gameplay for Halo Wars 2.
Alan Wake 2 is shown, exclusive to Xbox One and Windows 10.
Microsoft gets deal for big game on Xbox One (Like Resident Evil 7 or something like that).
Next Forza game is shown, game is on Windows 10 and Xbox One. (All future forza games were confirmed for W10 anyway).
Gears of War 4 gameplay demo.
Microsoft announces it has opened a few more first party studios, concepts of new games being developed by them are shown. (This is more a personal hope of mine, Microsoft really needs more first party studios).
Throw in a few more surprises here and there that I can't think of right now.
Sony:
The PS4K is real, launching for $400 holiday 2016, extremely useful for the PSVR somehow. (Like better framerates, resulution, etc.
PSVR is shown a lot more and will be the PS4K's best selling point.
New Crash Bandicoot game is shown, either a reboot or sequel. Launching in 2017 for PS4.
God of War 4 will be the final game shown in the Sony Conference, will be played on a PS4K and the game will look insanely good graphically. The leaked Norse setting photos end up being real and there will be a gameplay demo. Releasing with the PS4K Holiday 2016.Horizon: Zero Dawn, Dreams, etc all get gameplay demos. Launching in 2016 as well.
Sony Bend's new IP is shown off.
The Last of Us 2 quick teaser, but no gameplay as it's not ready yet and they wouldn't want to take away from Uncharted 4 which will only have released about a month earlier.
The Last Guardian is shown again, releasing in 2016.
Kingdom Hearts 3 trailer is shown, has Star Wars worlds and can use a lightsaber-ish keyblade.
Agent is finally re-shown as a PS4 exclusive.
Add in a few more surprises I can't think of right now.
Others:
The next Call of Duty for 2016 from Infinity Ward will be going back to the Modern Warfare series and will be Call of Duty: Modern Warfare 4.
Battlefield 5 rumors of taking place in WW1 are true and the game looks really good.
Watch Dogs 2 is shown from Ubisoft. No new Assassin's Creed is shown but is mentioned briefly in the conference.
New Sonic game is shown for the 30th anniversary, that game is similar to Sonic Generations in gameplay.
Titanfall 2 is shown, has a proper campaign this time.
Rockstar announces either new Red Dead game or Bully 2.
I basically wrote a novel for all of you, because the more I was writing this the more I was getting hyped thinking about what could be at E3 2016 and how we're only 2 months away.