As for the message, my understanding is that ethnic Fijians have always been i-taukei and Fijian, and they always will be. The only change is that now all citizens are legally Fijian.
Just as in New Zealand where there are Maori New Zealanders, Pakeha New Zealanders, Chinese and, yes, Fijian New Zealanders, Fiji will now have i-taukei Fijians, Rotuman Fijians, Solomoni Fijians, Kailoma Fijians, and so on. In some situations Maori will say they are Maori; and in others New Zealanders. Ethnic Fijians will be i-taukei or Fijian as the situation demands.
The Decree is about promoting national identity and a sense of belonging for all Fiji citizens. No one loses anything. All should gain.