I hope they release it on the 5th! The anticipation's killing me!
As far as what I'd like to see on the design:
I love the current look of the computer and hope they keep it. If they add the black lining like the current iMac, I'll probably buy a current generation, even with the lower specs because i HATE the look of the new iMac. However, I would like to see some slight changes like the magnetic latch, the mutitouch trackpad, and maybe a new keyboard (don't really care though, just want it to be ambient lit again). Besides that I just want to see hardware upgrades. As far as the likelihood. well...
Considering the rumors that the new ones will include the trackpad, that would imply a slight redesign, in which I hope they add the magnetic latch. However it would make more sense for Apple to change the design on the Montevina release this summer because it will be a bigger step. It makes even more sense for them to do a redesign when they switch over to Nahelem. I've heard it requires a different design, and so why change a computer's design, only to do so months later. This is probably when we'll see a big form update. I personally like the current design. I don't think its outdated. My only two problems with it are the latch and the plastic edging around the whole thing seems a bit fragile. And well, maybe make the aluminum a little sturdier because I've heard of people bending it.