"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
HDMI Announces USB-C to HDMI Cables for 4K Displays and TVs
The new specification will lead to the release of simple HDMI to USB-C cables that support the full range of HDMI 1.4b features, including 3D, Ethernet, and CEC. Connecting an HDMI-enabled 4K display or TV to a 12-inch MacBook currently requires using Apple's $79 USB-C Digital AV Multiport Adapter.
Thunderbolt remains the more popular I/O protocol for connecting 4K displays and TVs to Macs, since existing models are unable to drive 4K displays or TVs at 60Hz over HDMI by default. HDMI-enabled 4K displays and TVs connected to a 12-inch MacBook via adapter, for example, only support a 30Hz refresh rate.
In addition to the 12-inch MacBook, Apple is rumored to release updated MacBook Pro and MacBook Air models featuring USB-C ports with Thunderbolt 3 as early as October. Those notebooks would support HDMI to USB-C cables, providing Mac users with another option for connecting 4K displays and TVs.