I was wondering when this thread was going to get posted.
So, prediction time!
Microsoft: Probably another casualfest with Kinect. I just don't see how you can do anything hardcore with it. Hardcore games need precise control that you just can't get without buttons. I'm also going to go out on a limb here and say MS will introduce its own gaming portable to compete with the 3DS and NGP. A staff member of NintendoWorldReport (the same site that broke the Pokedex 3D story earlier today) teased that Nintendo isn't the only company with some handheld-related surprises. He's probably more likely referring to Sony, but MS has been conspicuously absent from the portable race for two generations now. Anyway, what's E3 without some wild speculation? Well, bam there it is! A new console might be teased along with a few small details in an attempt to steal some of Nintendo's thunder, but that's the most we'll get on that front.
Sony: NGP name and price reveal. I'm predicting about 299 US dollars to live la Vita loca. I can't see it being too far out of the general price range of the 3DS, and Sony is no stranger to taking a loss on system sales. Doubt we'll be hearing about the PS4. Microsoft might be willing to push out their new console to compete with Nintendo, but I see Sony sticking with their promise of a long console cycle since pushing out the PS4 too early and selling it at a loss is bound to do massive damage to Sony's budget. Although it'll probably be 7-8 years instead of the 10-year cycle they promised, putting the PS4 in 2013-2014.
Nintendo: It's pretty unanimous that Nintendo won E3 last year, and chances are, barring any major screwups, they'll repeat. You just can't compete with a console unveiling. I think this year's show will be similar to last year's. Right off the bat we'll get details of Mario 3DS, followed by an onslaught of Wii/3DS game details. Probably a release date for Netflix on 3DS. 3DS game trailers will become available via the eShop so they can be seen in 3D, but considering the fact that Nintendo tends to release online content on Mondays, we'll probably have to wait a week for that. The unveiling of the Wii2 / Cafe / Stream / Feel / Whatever they're calling it today, will come last and will be just as epic, if not moreso than the 3DS unveiling. Pikmin 3 has been teased for far too long and there has to be some reason for the delay, so I think it's a safe bet it'll be for the new system. I still doubt the touchscreen rumors. 6 inches is huge, and we heard the same song and dance before the Wii Remote was unveiled. Heck, I remember commenting on the Revolution touchscreen rumors on this very forum. Then again, as crazy as the rumor sounds, if anyone can pull it off it's Nintendo, and I can't wait to see what they have to show. My body is ready.