User blog comment:Sky-Dragoon-Twilight/Weisslogia and Skiadrum, Alive or Dead?/@comment-25849146-20141211044435/@comment-7418318-20141211103614

I hope they'll soon reveal why the Dragons were hiding (no matter where it was) in the first place.

Did they have some kind of prophecy foretelling the activation of the Faces? Was it because of E.N.D.? Was it for some other reason (like hiding inside their slayers slowing their aging process)?

Considering how Igneel was at the very least able to hold his own against Acnologia for quite some time before Face went off, I think they could have defeated him if all the Dragons worked together, so I doubt they hid from Acnologia.