Voidal Resonator should be a flying mount.

[Xieveral]

I doubt that existing mounts will fly in Heavensward, it would take away from the value of the new mounts in 3.0 to have any 2.0 mounts able to fly.

Also, IIRC they clarified the resonator's 'flight' capability suggesting that it uses it's legs to hop/jump and flappy wings to stay aloft, but cannot attain any altitude because it's more of a 'puddle jumper' rather than a soaring flier.

Chocobos are built like ostriches and shouldn't be capable of flight, yet they will be in Heavensward. I don't see why the same wouldn't be possible for the resonator.