My theory regarding the new MacBook design.
As it stands right now, the MacBook is $200 cheaper than the entry level MacBook Pro, that $200 gets you more battery life, an SD card slot, aluminum enclosure, LED backlit screen, better screen, backlit keyboard, and a faster processor. You are getting a lot for that $200.
So, they are either reducing their margins on the MBP or upping their margins on the MB.
IMO, there is very little they could do to the MacBook that wouldn't close the gap between it and the MBP except one... make it smaller. What if they put in a 11.6" screen or something, make it its own class again, a definitive difference between it and the MBP. Throw out the optical drive to make room for the larger battery and to thin it down some, smaller screen, same res, same size trackpad (minus the button) but make it the same as the MBPs where it is the button... I think that would work, and I know that I would be tempted, even if it kept the same price point.