Michael Buckley has gone AWOL

The last several times I've checked Amazon for news of the ninth and final Sisters Grimm book, the only thing that's turned up has been a book about Capital Tax Acts. I've managed to remain calm, because books occasionally fail to turn up until shortly before their publication dates, and Michael Buckley has been pretty consistent about publishing in the spring... until now. (The horror!) Amazon's Michael Buckley listing has finally been updated, but with the publication date for Nerds #3: The Cheerleaders of Doom, which isn't out until September. Does that mean we won't see the last Sisters Grimm book until next fall/winter? How am I supposed to WAIT THAT LONG?