A PDF-format repair guide was accidentally posted on Apple’s website. It detailed how the Airport Extreme Card would be replaced, and it specifically said “Late 2008” MacBooks and MacBook Pros. It’s been pulled since then, but did illustrate that the core components would be shared between the consumer and professional-oriented laptops.
AppleInsider also had news and photos of what are claimed to be components of the new laptops, including news that FireWire may not be on the consumer-oriented MacBook. This would be bizarre given the price of video cameras has been dropping, while Apple has been releasing software to allow customers to work with HD video (which is best done through FireWire). Even their consumer-oriented iLife allows you to work with HD video.
The photos show that the MacBook is probably moving to an aluminum enclosure (similar to the iMac’s move to aluminum).