User blog comment:SayuriDarling/Rick Riordan's Q&A for Goodreads/@comment-10901795-20150906105110/@comment-15860919-20150906105547

Addressing the question about Leo and Calypso, I'm pretty sure he was rubbing in the fact that he's not going to tell us. Or maybe there will be a small cameo, like Magnus seeing a metal dragon flying in the sky and deciding to ignore it.