From what thuway was saying (and I really respect his silence in regard to details), it seems to me (and i could be reading his comment totally wrong), that this event will be detailing the PS4 and it's launch. So we'll get the console detailed, controller, OS, Services and launch games + dev partnerships touched on. We may even get a launch window.
Then I'm expecting E3 will be the time the games themselves get the limelight, and it will be at E3 we get the big announcements like ''Versus XIII on PS4!!!'' and ''The Last Guardian on PS4!!!'' as they will likely be released after launch.
I will say this. I'll be fucking pissed if we've come this far and some inconsiderate moron leaks everything. I mean is 5 minutes of fame really worth spoiling such a big event for the industry?