A random person Derpibooru was digging around and ran into a little excerpt from the upcoming Pinkie Pie Rockin' Palooza Party book via Google's mini-previews on search, and amazingly enough, this single sentence has completely named the entire Pie family. The actual book page doesn't reveal anything else as of yet, and I am not 100% sure how those lines are excracted, so I can't say this is set in stone right now. It does seem possible though!
Thanks to Masem for the heads up.
