Is it true that there is only going to be four books?
That doesn't sound right to me.
this is where i got the impression from:
"I now have a title for the next volume (4) in the Power of Five ¦although if you dont like it, I can always think again. It's going to be called CITY OF THE DEAD. Most of it is set in Hong Kong, as you know, and I hope to go out there later this year for research. I've got about 50% of the book in my head. Did any of you guess what Scar's secret power is? There are clues in NIGHTRISE.
It's going to make a great final chapter with devastation on a massive scale ¦in fact I'm really looking forward to writing the end of the book which is always a good sign. It makes me keener to start writing the beginning."
Taken from
http://anthonyhorowitz.com/newscentre/page/2/