According to an interview on a french website:
!Google Translated!
"In the current version, flying with your drake is limited. It is an element that you can improve by unlocking elements (speed). The ability to fly from any place to another in Dragonflight will require completing certain prerequisites. Blizzard continues to believe that the best way to experience expansion content is from the ground and not by allowing players to fly from point to point on day one."
Maybe there is some context lost in the translation, but it seems like we won't be able to fly while leveling.