There have been several blogs (see here and here) recently talking about the second edition of Effective Java, expected to be released at 2008 JavaOne Conference. As of this blog entry's writing, Amazon.com's "Look Inside" feature for the Second Edition still links to the table of contents for the First Edition. However, the Pearson web site does link to the new table of contents for the Second Edition.
The Pearson web page's listing of the Effective Java Second Edition Table of Contents shows 78 items in the Second Edition (the First Edition had 57 items). There are entire new chapters in this edition to cover features introduced with J2SE 5. For example Chapter 5 is called "Generics," Chapter 6 is called "Enums and Annotations," and the Concurrency chapter (chapter 10) appears to be quite different to cover the Java threading support.
The table of contents for the Second Edition certainly gives a good insight into what to expect in that edition. Another preview of this edition is available in the 2006 JavaOne presentation Effective Java Reloaded (TS-1512).