Wii 2 will be shown. Holiday 2012. This is Nintendo's chance to introduce us to it, but E3 2012 will be the one where they pull out the big-guns on software/content/announcements.
Will exceed everyone's expectations and yet scratch heads and be missing something integral (like still be using DVDs or maybe still require friend codes; some dumb shit).
Dark Souls will make me jizz my pants.
Zelda will finally get a release date.
Super Mario 3DS will be shown off, along with Paper Mario 3DS and Mario Kart 3DS and Zelda OoT 3DS. Hopefully there's an announcement of Majora's Mask 3DS, but probably not until they see how OoT sells. Third-parties will announce 3DS release dates (tentative or otherwise) to games like MGS3DS and Resident Evil. Maybe new announcements like Kid Icarus release date or a Smash Bros 3DS (not likely at all).
Work-in-progress titles for Wii 2 will be shown, but probably won't be playable besides some tech demos.
DS titles will still be announced and shown, including ones that just came out, but the focus will clearly be moving towards 3DS instead.
Microsoft's new console will be announced or unveiled, but not much details besides that. They'll focus on Kinect, Gears of War 3, and other shit I don't care about. Maybe that rumored remake of Halo.
Sony will focus on PS3 content, as usual, and show off their new NGP with more games. They'll focus on Uncharted 3, The Last Guardian, inFAMOUS 2, Twisted Metal, Resistance 3, and announce a few more games like Starhawk, or Sly Cooper 4, or David Cage's new game, along with a surprise or two (maybe finally show off Agent). NGP will show off LittleBigPlanet, Uncharted NGP, and more features about the handheld and how it will be incorporated with PSN and the PS3.
Since the hacking incident, Sony has started to take the PSN much more seriously, and it's likely that at E3 they'll announce more features for it that they will have been working on since now.
Lots of sales charts from Sony, since they like that. Probably not as many from Nintendo since they learned from their Cammy days.
Microsoft will have lots of boasting about Kinect, which is well-deserved, but like I said, idgaf.
Konami will not have a conference as epic as last year.
Games I'm interested in will get shown in more detail, like Assassin's Creed Revelations, etc.,
Square-Enix might finally show something for FFXIII Versus, but not much more than we've already seen. They'll be focusing on their other bullshit.
EDIT: Actually, one more thing. Lightbox is revealing Starhawk this coming Friday, May 13th. This is also related to the next GTTV episode, which will probably show gameplay of this.
So I forgot, that probably like before, Sony will announce new games before E3 for absolutely no reason.