This is my impression of what we'll see released at MacWorld. An extension of the tripod style, with a 15" wide-aspect display like the TiBooks and similar aesthetics to the Cube and Studio Displays. All the usual connectivity, with four USB ports because you can never have enough of those suckers. Pricing from US$1299 (let's be realistic here!)
A Quicktime VR of the new iMac can be viewed here.