Funny how we currently know more about Saturn, Celestial Dragons than Teach and Xebec(likely related to Teach.
Oda went out of his way to even hide Xebec during this flashback. On the other hand, he keeps portraying the Celestial Dragons evil side, and as a reminder, the Blackbeard pirates are in this arc as well, but are saved for later
The way things go, the Celestial dragons are bound to end up dragged from their lofty spots somewhere down the road and Teach will be there to claim the prize