First, it is common knowledge that Apple will update its MacBook lineup at the media event. It was originally thought that a $899 MacBook would be introduced. Images leaked online have revealed an aluminum case with single buttonless (but clickable) glass trackpad. According to Daring Fireball, the "new trackpad is similar to the Airs, in that it is bigger and supports additional multi-touch gestures. But unlike the Airs, the MacBook Pros new trackpad is made of glass, and is a button itself. You just press and it clicks."
The new MacBook Pro will not be available in matte-finish, only glossy. Due to production issues there will be no 17" MacBook Pro immediately available. The existing 17" model will remain on sale but with increased storage/RAM options.
MacNN indicates that two MacBook models (2GB/160GB and 2GB/250GB for $1,299 and $1,499, respectively) will ship and that the current $1,099 2.1GHz MacBook price will be dropped to $999 (without the updates featured in the new MacBooks).
The MacBook Air will reportedly see a larger 120GB hard drive and larger 128GB SSD option.
The $899 MacBook rumor is likely false and the SKU reflects the price of a new DisplayPort-enabled $899 24-inch LED Apple Cinema Display.
In terms of graphics the MacBook will use the improved NVIDIA 9400M GPU, while the MacBook Pro will also have a dedicated 9600M GT GPU for additional performance gains.