"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple to Update MacBook Air to Penryn Soon?
The external design is to remain the same, but the new MacBook Air is said to incorporate a new Penryn-class processor "from 2.0GHz and potentially beyond". To compensate, Apple will be including a higher capacity battery.
In fact, the new revision of the MacBook Air will draw it much more in-line with the current MacBook internals. Expect to see SSD prices in-line with the current revision, however the hard drive version of the MacBook Air will likely be upgraded to 120 GB, and optionally 160 GB, due to falling prices for 1.8-inch hard drives.PhoneNews is not a typical source of Apple rumors, but appears to have a reasonably good reputation.
The timeframe for such an update is also reasonable with earlier reports indicating that Intel was planning on a Penryn update to the custom MacBook Air processor. Several readers, however, had hoped that Apple would simply choose to utilize the more power-efficient chips at the same processor speeds in order to extend battery life.