Originally, JDK8 was expected in September, but with the developers having a lot on their hands lately for tackling security problems, it's been decided to push-back the release. Rather than scrapping "Project Lambda" for the next Java release, they have decided to push back the language update for months.
Project Lambda is the Java Programming Language initiative to support multi-core programming by adding closures and other new features to the language.
The delay of Java 8 was shared in this blog post by Mark Reinhold, the Chief Architect of the Java Platform Group.
Java 9 has also been subsequently delayed into 2016 as a result of this setback.