"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Apple Customer Survey Suggests Interest in 3G-Enabled MacBook Air

AppleInsider reports that a customer survey from Apple gauging user satisfaction with the company's new MacBook Air contains several questions related to 3G connectivity, suggesting that Apple may be considering adding the feature as a built-in option on future models.
Perhaps most telling are a number of questions in the survey related to 3G data use and connectivity. The MacBook Air comes with integrated Wi-Fi, but does not have a built-in 3G radio.
Apple's survey asks users whether they have connected their MacBook Air to a 3G network, how often they do so, where they connect to 3G, what type of device they use to connect to a 3G network (MiFi, USB device, or tethering with a cell phone).

Many users have continued to hope, however, that Apple builds 3G access directly into a future model of the MacBook Air in order to make it a self-contained always-connected portable machine. An Apple job posting in mid-2009 hinted at the possibility that the company was looking at built-in 3G for portable Macs, and a rumor suggesting just that surfaced just weeks later, although no such device has yet appeared.
While the MacBook Air received a significant redesign, including the addition of an 11.6-inch model, just this past October, observers are already looking forward to a rumored update to Intel's new Sandy Bridge processors as early as June of this year.