Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I think the Air has ruled a 13" Pro out. Since the introduction of the MacBook, Apple has regarded it as the iBook and 12" PowerBook successor.

The MacBook Air could have easily been made "Pro" class at the expense of being as thin/light as it is... seems like Apple want to branch out into new territory and attract more people that way.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.