Shaving too much weight and it'll get into MBA territory and I don't think apple would do that to themselves.
Really, why not? Let me explain and see if people agree.
Over the years, Apple has really been their only competitor or at least since I have been using them since 1993.
I remember when the Macbook came out with core duo processor in tow. People for quite some time thought it was nearly a Macbook Pro on many levels. But both laptops sold decently even though both cost far more than similar core duo PC laptops.
Apple could have used the core solo, still a good engine in its own right, in the Macbook for a long time, or forever, but Apple wanted what "we", the core cutting edge users on this site want. I recently saw some PC laptops still sporting the core solo in their laptops at Best Buy.
Look at the history of the iPod and iPhone. Each model totally make the one previous to it obsolete and they come down the pike faster than we can even predict they would. And the history of the lowering of price even trumps the respectable lowering in price of the Macs themselves.
What may happen with a sleeker Macbook