This years E3 will be pivotal for both Sony and Microsoft as they will look win consumers over with exclusive games, strong 3^rd party support, and exclusive content.  Going into this years E3 Microsoft has the most to prove, while Sony is looking to solidify their lead over the competition.  Before I go into the predictions themselves, here are a few key factors to consider:

-Microsoft still has several unannounced 1^st party studios.

-The Playstation 4 is currently outselling the Xbox One in all territories.

-Microsoft will be preparing to launch the Xbox One in new territories.

-Both Playstation and Xbox have had some Executives come and go. Jack Trenton left Playstation, Don Mattric & Marc Whitten both left Xbox, and Phil Spencer is the new head of Xbox.

Now, finally, I think that both Microsoft and Sony are going to have stellar E3 showings, the winner will likely come down not just to what is shown, but how it is shown, and how good the games end up being.

Sony’s Conference

Third Party Games

-Destiny Gameplay & Beta Anouncement.

-Assassin’s Creed Unity Gameplay

-GTA V Remastered Announcement

-Batman Arkham Knight

-FF XV Gameplay

-MGS V

AAA Exclusives (Already announced)

-The Order 1886 Gameplay

-Uncharted 4 Trailer, “coming 2015”

-Driveclub trailer & Release Date

-TLOU Remastered Trailer

Indy Games

-Show off one new promising Indy game

-Show off a bunch of indy games at once in trailer.

AAA Exclusives (Unannounced)

-Sony Bend New IP

-The Last Guardian Reintroduced

-Gorilla Games New IP Teaser Trailer

Non Game Announcements

-Talk About PS4 & PS3 Sales success.

-Talk Briefly about plans for Playstation VR and Playstation Now.

-Talk Briefly about Vita

-Talk about PS+ and Instant Game Collection.

-Playstation 4 Media feature updates and New Apps.

Microsoft’s Conference

Third Party Games

-Fallout 4

-The Division Trailer & Exclusive Content

-Call of Duty (unfortunately)

-Resident Evil 7

-Evolve

AAA Exclusives (already announced)

-Project Spark trailer & launch date.

-Sunset Overdrive Gameplay & Release Date.

-Quantum Break Gameplay & Trailer.

-Fable Legends Trailer& Beta announcement.

-Halo 5

Indy Games

-Below Update

-One new Promising Indy title shown.

-“We have over ‘x’ amount of devs. for ID@Xbox making ‘x’ amount of games for Xbox One.”

AAA Exclusives (Unanounced)

-Forza Horizon 2

-Halo 2 Anniversaryd

-New IP by LXP studio announced

-New IP teased by unannounced 1^st party studio

Non Game Announcements

-Price Drop in all territories for Xbox One, Kinect still included.

-Xbox 360 price drop in all territories.

-Games with Gold for Xbox One

-New Xbox One feature(s) shown off

**Notes:

-I don't have any insider information, everything you see above is pure speculation on my part.

-for thoes wondering about LXP, and the other "unanounced studio" I mentioned for Microsoft's conference, Microsoft anounced last E3 that they had started 5 new 1st party studios.  LXP stands for Leap Experience Pioneers, and is a name of one of thier unanounced studios that was leaked.

-Also, while it is possible that Sony will show the delayed exclusive Deep Down at E3, I personally don't think that they will as it curently does not have a planned western release, and did not show up at last year's E3.

Sony:
How the ps4 will succeed
How the Vita will fail
The release date for the Last Guardian will be 2020

MS:
How the X1 will be in second Place
How little they care about PC Gaming
Original TV Shows

I still believe UC4 is coming this year. DClub TOrder are nice but UC4 is the holiday Juggernaut, no amount of marketing hype whatever will make those two even half of what Uncharted is.

Sony migth show more then they normally would, they will want to counter any positive reaction to MS stuff they can.

GT7 teaser, Meadia Molecule game and God of War (ps) 4 would be a great salvo.

Sony will have at least 2 new game announcements as well as some big plus games coming within the year I expect. They'll probably have a multiplat announcement at their conference (Mad Max, FF15, and KH3 last year). Before those probably some gameplay from stuff we haven't seen it from or haven't seen it from for awhile.

Sony:
Uncharted 4 - Holiday 2014 release date
The Last of Us Remastered
Driveclub
The Order: 1886
The Last Guardian PS4 version
New IP
Next game/s in a series
PS4 sales
PlayStation Now
VR

Microsoft:
Japanese exclusives
Halo 5
Halo 2 Anniversary
Project Spark
Sunset Overdrive
Quantum Break
Non Japanese exclusive/s announced
Xbox One sales
Teh powa of cloud

Third Party games Sony and/or Microsoft will mention:
Destiny
The Division
The Witcher 3
COD 2014
GTA V PS4/Xbox One
Batman: Arkham Night
Metal Gear Solid V
Kingdom Hearts 3
Final Fantasy XV
Resident Evil 7
Assassin's Creed: Unity
New games

I want only one game reveal from the big three.

Sony - Legend of Dragoon 2
Nintendo - Metroid Prime 4
Microsoft - Banjo 3

Give me these games and it will be the greatest E3 ever.

Order of likelihood greatest to least is Nintendo, Microsoft, Sony on that one.

Let me dream. 

Sony
-Will Reveal several games coming within the next year: New RPG(possibly WRPG), Crash Bandicoot's return, Exclusive Multiplayer Action Game
-World Reveal of some 3rd Party Game that will pretend to be exclusive for the show, Resident Evil 7
-Older Games Detailed: The Order 1886 new trailer/info, Uncharted PS4 detailed and dated for holiday, Destiny, DriveClub, The Last of Us Remastered
-New Features Detailed: Morpheus VR further explained/hint at pricing. DriveClub demonstrated with VR. Playstation NOW fully revealed and slated to release sometime around conference, allows games to be easily demoed from any system.
-Brief Spin of Vita Situation: Show off Freedom Wars, Soul Sacrifice Delta, Gravity Rush 2, Murasaki Baby Oreshika: Tainted Bloodlines. Reveal FF Type-0 coming to Vita as well as some other huge 3rd Party title (Another AC or MH). A plethora of indie titles re-affirmed. All probably perfectly packaged in a single montage.

Microsoft
-Will Show Several NEW games. At least 2, most likely slated for this year.
-Re Affirming older stuff: Quantum Break info/gameplay, Sunset Overdrive release 2014, Halo 2 Anniversary Holiday 2014
-Will Reveal TV based feature info: Halo TV Show, Exclusive Apps.
-Real of 3rd Party Multiplats: COD, BF, AC, Batman, The Witcher 3, KH3, FFXV, Elder Scrolls Online
-Will reveal a VR initiative to rival Morpheus. Used in junction with Kinect.
-I fully expect some theatrics to detract from their show's weak points
-Speech about how they have changed their stances and pursuing indie and 3rd party vigorously.

XBO dev kit annoucement is what i want.