I won't see Nintendo's Conference live, but I hope to see Sony. I really have no thoughts about what each company will show off simply because I don't own a Wii or PS3 as of yet. Sony has the history of really going out into the "fall asleep zone" with their Conferences. I hope they've learned that pounding out numbers for 20 minutes straight just isn't the way to do things. Last night Microsoft had numbers here and there, but they mostly let the games talk for themselves (the smart thing to do). Sony should do the same thing.
Unfortunately with Crazy Ken Kutaragi no longer with Sony things won't be nearly as insane probably. Kaz (Mr. "Rrrrrrrrrrrrrrridge Racer") is still around though, maybe he'll have some good zingers. Sony doesn't have a whole lot of 3rd party stuff to show off that doesn't run faster on the 360 (EA Sports games) or doesn't come out before the 360 version (Medal of Honor: Airborne for example). Yes, there is Metal Gear Solid 4 and Final Fantasy XIII to show off, but neither game will see the light of day before 2008 in my estimation. They do have one 3rd party game to show off and that would be Burnout Paradise since it is supposedly being built on PS3 first and ported to the 360 - the only EA game I know of that is doing that currently, most are being done on the 360 and ported to the PS3 (EA Sports games for instance).
Instead Sony will have to rely on their 1st party offerings such as Ratchet and Clank Future: Tools of Destruction, Uncharted: Drake's Fortune and Killzone 2. They will also probably spend most of their time talking about Home and I think it will be a tough sell to people. It sounds cool, but what are we actually going to be able to do with it? I hope they answer those questions.
On the PSP side maybe they'll show off the Slim design and give a release date and price for it. I'm not too up on PSP releases, so I don't know if there are any big games upcoming for it or not.
On the Nintendo side they also don't have a lot of top notch 3rd party offerings coming, most of their sales will come from their own internal developers. Metroid Prime 3: Corruption (coming in August), Super Mario Galaxy and Super Mario Kart will probably be shown. They will also probably show a lineup of mini-game filled titles that are the bread and butter of Wii releases. Those games are what brings gamers of all ages together, I just don't know how long Nintendo can hold onto that lightning in this case.
On the DS side everything is rosy of course. I want to see more of Phantom Hourglass and many of the other games upcoming. Nintendo will probably also throw around numbers and they'll sit somewhere between Microsoft and Sony in how much time they spend on them.
Both Conferences should be interesting though.