The LoRaWAN1.0.3 now fully supports unicast & multicast classB devices.
The classA and classC sections are unchanged compared to LoRaWAN1.0.2 with the exception of a new MAC command "DeviceTimeRequest" used to synchronize the real time clock of a device.
For devices operating in classA or classC, there is no need to upgrade to LoRaWAN1.0.3
However, If you plan to use classB in your devices then you should use LW1.0.3
The LoRaWAN1.0.3 ClassB section is forward compatible with the LoRaWAN1.1 classB.