Ignoring the fact that this has nothing to do with localization, it was never stated anywhere that the sacrifices were "new races". All the known races that live on the planet present day are races that came into being after the Sundering had already happened.
Primals temper according to their purpose, and Zodiark's purpose was always "salvation". Nothing will happen if there is no situation where the people need salvation. Zodiark would be doing pirouettes in orbit and life would probably go on as normal. And also, according to the game itself, the "tempering" that Zodiark supposedly did to the Ancients was very different from the tempering of the crude Primals of the tribes whose summoning process was intentionally introduced to them in a botched fashion. It is supposedly much milder and more like a slight nudge.