At the same time, there are native races to Eorzea. They're just not the playable ones. The Kobolds and Amalj'aa are endemic to Vylbrand and Paglth'an, their histories tied intrinsically to the lands their cultures and biologies adapted to, and the Sylphs have been present in the Twelveswood for millennia longer than any Elezen or Hyur. You are right about the playable races having migrated, but that doesn't really answer or provide much help on the question of whether the Meracydian dragons predated the Dravanian ones. All we have to go on is the fact that the former is recorded as having been present three thousand years ago, while the first mention of the latter is from two thousand years after that. But we also cannot rule out the possibility that dragons could very well have arisen in Dravania before, or independently to, the Meracydian dragons.