If you have a look at the cover, it says "Exams 310-XXX & 310-XXX", the publisher (Osborne) does not even mention this book (yet)... Maybe there will be a new developer exam in the near future, but I don't think that Amazon will know first
I understand that Sun are talking about a new version of SCJD, and it is currently slated for before the end of the year. But with such a broad "due date" you cannot guarantee when it will be formally released.
Sun usually have beta exams before the final releas, and Sun Education often announce the beta exams in JavaRanch in the appropriate forum. Which means that it is likely that it will eventually be announce in this forum.
Most publishers do "pre release" announcments to online book retailers (such as Amazon), so it is common to see a book listed on Amazon before it is listed on the publisher's website. Similarly, since this is a pre release announcment, it is not unusual for the book to be listed on Amazon before the exam is listed by Sun.