Socom 4 was announced like four months ago, and on top of that, both it and LBP2 are coming out this year. Announcing them early in the year is like Sony announcing Resistance 2 and MotorStorm: Pacific Rift back at the start of 2008 as they both came out that Fall.
Killzone 3 was announced early, yes, but if you notice, it's an SCEE title. I don't think we've seen an SCEE title announced at E3 since Killzone 2 and MotorStorm back in 2005. It's become a fairly SCEA-centric affair, with the occasional SCEJ title that has worldwide appeal showing up (The Last Guardian, Gran Turismo). If you notice, in 2008 the only new titles anounced at E3 were SCEA titles (MAG, God of War III), and in 2009 it was all SCEA stuff aside from The Last Guardian, Agent, and Final Fantasy XIV. No SCEE titles in sight.
This year I think we'll once again see new SCEA titles announced. Aside from InFamous 2, either Starhawk, Syphon Filter, Twisted Metal, or something new, alongside demos of games from the other branches. And yeah, we know about InFamous 2 already, but a picture of a Game Informer cover gives us no more information than we had before. All we know is that it's coming, but it'll actually be revealed at the show.
So yeah, I expect a few new games from SCEA and maybe something from SCEJ. Aside from that, expect lots of demos. Killzone 3 and LittleBigPlanet 2 at the very least. I get the feeling the Killzone 3 demo could be the Uncharted 2 of the show.
Edit:
Forgot about Agent. I would expect them to finally tell us what it's all about at the show as well. Probably alongside a gamplay trailer if not an actual demo.