The most self-evident change between Apple's current MacBook lineup and the new models expected next week are the side expansion ports.
Both the MacBook and MacBook Pro that appear to have been photographed have extremely thin side areas which are just large enough to contain the ports themselves -- thin enough that Apple has had to shunt the port labels to the side. While neither system will be quite as thin as this, as Apple is believed to be using a tapered bottom that will add slightly to the height, the reengineering may contribute to a design which is predicted by some to be thinner overall than earlier models.
Port layouts have also changed, though without better photos and a view of both sides it's difficult to tell how many elements have been added or removed. Again, the MacBook Pro has potentially switched to mini-DVI output instead of the full connector from Apple's professional notebooks of the past several years, though why this would be chosen remains a mystery. Historically, Apple has opted for proprietary connections for its displays when space for other ports is an issue; the quintessential example of this has been the micro-DVI connector necessitated by the thin, small expansion door of the MacBook Air.
The next MacBook Pro's top and left sides.
Apple's rumored 13-inch MacBook as seen from its top and sides.
But while the 13-inch MacBook's top layout is widely expected to match that of its similarly-sized ultraportable sibling, extending to a larger trackpad, the MacBook Pro will carry more tangibly unique design changes besides the new keyboard tray. The speaker grilles bordering the keyboard are more finely perforated than today's system and, notably, no longer run to the edge of the notebook as they do now -- though whether these differences are for practical size purposes or simply a stylistic change isn't evident at this stage.
What may be clearer, however, is Apple's design direction for the top of its notebooks, which may have been tipped off by the company's own invitation for the introduction on its corporate campus. An observation at Boing Boing notes both that the edge of the display isn't that of the MacBook Air but also that the logo isn't necessarily proportioned correctly for the shadowed image to represent a 15-inch MacBook Pro.
The MacBook in Apple's press invitation, with the logo used as a guide for size. | Credit Boing Boing
Using the size of the logo on a present-day MacBook Pro as a reference, the site estimates that the logo is too large relative to the borders of the lid to represent a system with a screen larger than the 13.3 inches of the standard MacBook.
Apple in the past has changed the size of its logo and isn't necessarily using an actual future system as a template, giving some leeway for its teaser image to represent a different model or none at all. Still, the image is potentially the Mac maker's most direct hint yet of its upcoming design direction.