It's coming... The next Ethan Warner novel is due to hit shelves on November 8th, 2012 in the UK and Commonwealth. ( Readers in the USA and Canada will have to wait until early 2014, due to the slower hardback-then-paperback publishing process out there. )
Here's the cover and the back page - I think it looks awesome! The cover for Australia is slightly different and conforms with their own series of designs for the series.