Predictions - Slight PS4 price cut to undercut the X1 and keep the momentum going. Demon's Souls 2 shown in its full glory on stage at Sony's event, with a release window mentioned.
X1 will have a strong stable of must-have games to continue the momentum they've picked up from the price drop, putting it into serious contention with the PS4. Not sure what they'll have, but stuff like Sunset Overdrive is sure to impress.
For Nintendo, I think they'll have a strong showing of Wii U games, specifically a few big franchises from their stable. They'll also show or announce some third party developed stuff using Nintendo properties. NFC figures will also show up for specific Wii U games to try and capitalize on the Skylanders market.