I have a feeling Apple will have a trick up their sleeves at the March 7th event.
I think one of these situations will come true:
1. iPad Mini alongside iPad 3, priced at $349
2. Apple TV, whatever that means
3. All-new Macbook Pro
4. Aperture/iPhoto/MS Office for iPad
I'll guess that #3 won't happen, as it's an iOS event. They may spec bump some of the Macs on the 7th, but they won't talk about it at the event, just release a new models when the store comes back up. Even that seems highly unlikely.
I'd say #4 is a 50-50 for Office. We've seen the leaks, and denials, so it has a good chance at getting a brief demonstration. I would also say there's a slight chance for some other Apple app to make the jump - iPhoto seems like a good bet if the iPad 3 has a much improved camera.
I have a feeling that the Apple TV is going to be updated. Whether it's just a small bump to the A5 SoC, enabling 1080p support or a full fledged new product (that is to say, an actual TV) I haven't got a guess. Could be both. I could see Apple doing a new AppleTV with slightly bumped hardware (A4->A5) along with lots of new software features and then offering it as a 30", 42", or bring your own TV model (what they have now) or something/
As for #1, I have a whole host of theories. I would put money on there being 2 distinct models of iPads this year. Most likely, they keep the iPad 2 around as a low price into model; possibly like the iPhone 4, offering it in a limited storage capacity model only. Say 16gb iPad 2 at $399, 32gb @ $499, then jump to iPad 3's at 32/64/maybe 128 at $599/699/799, or something.
But, I think there's a decent chance there will be a completely new device as well. An 8" would be ideal for me, and at $349 would probably destroy the Kindle Fire, the only credible iPad threat thus far. Or, perhaps an iPad 2S with a slightly modified SoC and feature set slimming it down even more. If the iPad 3 is going to get bigger then perhaps it would make sense to do an "iPad Air" line that is even smaller, at the expense of some features. (though, in that case, I would prefer the iPad Air to be an 8" model).
Either way, I'm pretty excited about next week! I've been rocking my iPad 1 since launch day and it's due for replacement. I'm going to be handing it down to my 4 year old for his birthday (with an Otterbox!) on the 6th regardless, so I'll be iPad-less (sort of - I have a first gen from work as well

)! If they do an 8" model I will be pre-ordering... if not, I might hunt for a good deal on an iPad 2, or maybe even check out the Kindle...