Nintendo's going to have a new 3D Mario, new Smash, Retro's new game, and most importantly in my opinion, finally a reveal trailer for Bayonetta 2 that I expect to be absolutely unbelievable. Also follow up footage for Wonderful 101, Pikmin 3, Xenoblade 2 (why even bother calling it Project X? Lets get real here), admittedly unexciting but significant Mario Kart U unveiling, and probably some Zelda which I couldn't give a single fuck about, but I know many people do.
Nintendo's got this on lockdown with what I expect to be their best E3 in... Well, EVER actually, provided the games don't look like boring shit. At the very least I know Platinum will absolutely bring it with Bayonetta 2 like they always do.
I don't expect much in the way of exclusive hardware from the other two, I honestly just don't see it. On Sony's side we'll probably see Versus turned into FFXV which will be amazing, and MIGHT see Last Guardian on PS4 which would certainly be fantastic, but beyond that I think we'll be left with follow ups for Second Son/Killzone/Knack/Drive Club, only the middle two I'm particularly interested in. Xbox may or may not pull something huge on the software end, but the only remotely interesting thing I'm confident in is a Halo teaser.
What I'm really interested in is the Vita, though. Do or die time for the US and all that, I could kill for a Gravity Rush 2. PS3 will have a surprisingly good showing as well.