"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
PowerBook Updates Too?
The PowerBooks will still sport G4 processors, however, and the new high end will fall at 1.67GHz, while the 12" will be bumped to 1.5GHz.
The new PowerBooks will feature Bluetooth 2.0 support and minor storage and memory updates.