"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Replacing the MacBook RAM, Hard Drive (Video) and Benchmarks
Both the MacBook's RAM and Hard Drive are accessible through a panel under the battery and the process has been detailed in this Video from MacWorld.
MacWorld also provides the first benchmarks of the new MacBook, comparing it to the G4 iBooks it replaces as well as the current MacBook Pro and iMac.