Hatsumi Sensei is releasing a new book called Ninpo Daizen . It will be available from Kodansha April 25th, 2013. It is currently only published in Japanese but will eventually be translated into other languages at a later date.

Ninpo Daizen

Here is an overview of the included chapters:
First Chapter - Bufu and Ninpō
Second Chapter - Togakure Ryū Ninpō
Third Chapter - Ninpō Hiden
Fourth Chapter - Ninpō, Hizō no Densho {Treasured Densho of Ninpo}

Here is info on the book from Kinokuniya Japan: