Preview at WWDC likely in June, followed by September launch.
Apple Document Confirms MacBook/MacBook Pro (Late 2008)
Apple has published a support document (PDF) specifically for the "MacBook/MacBook Pro (Late 2008)" models. Besides the name, the document is not especially revealing. It appears to be a service document when replacing the display on the new MacBooks.
Before installing the replacement display, install the AirPort card on the display assembly. The display assembly does not come with the AirPort card installed.Apple will be announcing the new MacBook and MacBook Pro on Tuesday, October 14th at a special media event.