Good question. It seemed to me that they went and replaced the backlit keyboard with the audio speaker enhancements. Who knows? Maybe they'll compromise this time. I do have to admit, the current MBA has incredible built-in audio. In fact, by far, the best stereo spacial audio I've ever heard out of any laptop speakers, and you don't even see them.
Though I do still wonder why give such audio to the main laptops people would least use for built-in audio. You'd figure the main Air-specific audience would generally be traveling in such way that they'd prefer to be courteous and use headphones, mostly. I'd figure light above speaker quality, but maybe that's just me.
(I think someone in the hardware team, must've wanted to sneak-in stuff to turn the MBA into a minor gaming machine, that time. Hey, let's slip in that, better than average, laptop videocard into a ultra-portable and some kick butt speakers in the thing. They wont know what hit them. And by the time the smoke clears, I'll be playing Portal 2 full speed on this little rig. Uh oh, someone's coming. *Ahem* We really were just going for something that could be real snappy when running the OS. That's what we're shooting for.)