But the news is officially "out there" now, so I can FINALLY tell you that yes, THIS IS HAPPENING:
Yes--that's right. EVERBLAZE is not the end of the KEEPER series. THERE WILL BE A KEEPER #4--which has no title yet, or any official plot details (it also, um, hasn't been written--but details, details. I'm working on it!)
Sadly, that's pretty much all I can share at the moment. It's hard to talk about book 4 when you guys haven't read book 3 (definitely don't want to spoil anything for you). But I can show you the official deal announcement from PM, which does tell you one sentence about it:
Shannon Messenger's book 4 in the Keeper of the Lost Cities series, a young girl with secrets buried in her memory must realize the full power of her abilities if she is to infiltrate a dangerous new society to prevent a deadly conflict with the potential to destroy the Lost Cities and the future of her kind, again to Liesa Abrams at Aladdin, for publication in Fall 2015*, by Laura Rennert at Andrea Brown Literary Agency (NA).firstname.lastname@example.org
I also want to give a HUGE "thank you" to each and every one of you for the love and enthusiasm you've shown this series. My agent, editor, and the whole team at S&S have all been amazingly supportive, BUT, we still wouldn't be adding another book if you guys weren't such incredible, awesome readers!!!
So thank you for the fandoms you've started, and the fan art you send me, and for telling your friends and family and librarians and teachers. Bit by bit you guys are helping this series grow, and you have no idea how much I appreciate it. I can't WAIT for you guys to read EVERBLAZE this November, and I can't wait to write book 4.
And on that note, I should probably get started--TO THE WRITING CAVE!!!!
*in PM it was incorrectly listed as Fall 2016, so I amended it here.