I'll buy a Wii U if their first party lineup looks amazing, which it has to be if they want to survive. Third party support is basically dead.
Microsoft: lol. There's practically nothing they could announce that would make me buy this junk. That said, I expect their conference to be decent with much more emphasis on games. Since third party games will look and run better on PS4, they'll have to show a lot of first party and third party exclusives.
Ubisoft: Theyad a great showing last year and I look forward to seeing what they have this year. Most likely Watch Dogs, AC4 running on PS4, and hopefully some surprises.
EA: New Need For Speed should be cool and looking forward to BF4 multiplayer footage.
Sony: rumors are pointing to Sony having a really strong showing. Looking forward to the gameplay demo of Destiny as well as any first party stuff. FFXV is said to be PS4 exclusive. Also we'll finally get to see what the system looks like. Trying not to get overhyped. :p