I doubt it.
Firstly, ARM still lacks the raw power to make any headway in the desktop space, and since professional audio/video production applications are a part of Apple's Mac platform (Logic and Final Cut, anyone?), it wouldn't make any sense to re-engineer software just for a downgrade.
Secondly, Intel is Apple's b*tch. Really. Apple gets Intel CPU and chipsets to market pretty much before anybody else. Furthermore, there are CPUs in Apple Macs (like the MBA) that you simply won't find anywhere else, as they're custom built for Apple. Why would Apple mess with that sort of arrangement just for the sake of battery life?
Also, keep in mind that Apple is more or less in cruise control in the desktop space. Macs are slowly becoming a smaller and smaller part of Apple's profit share because they've moved on from trying to innovate there and have focused more on where the ball is going next: Tablets, smartphones, and other relatively powerful mobile devices. I mean, just look at the previews for Mac OS 10.7 Lion. How much more trivial can a new Mac OS X release get?
2011 15" MacBook Pro Ci7 2GHz, 8GB DDR3-1066, Intel 510 256GB SSD