Oracle has posted in the jdk8-dev mailing list the JDK 8 milestone and release dates for review and feedback. Following dates for the JDK 8 development milestones have been proposed.
Details for each milestone has not been specified, but will be posted as soon as it is available to help the early testing process. M6 is expected to be feature complete (FC). This is when all features and new test development would be completed. JDK 8 is targeted to be released by September 2013. This is to give at least as much time to stabilize JDK 8 as was needed in JDK 7.
Between M6 and GA, the tolerance for changes will decrease in steps. General bug fixing is allowed from early February till early April 2013. By early April 2013, only P1-P3 bugs will be fixed. By mid-June 2013, only showstoppers will be considered.
Component JSRs will not need to follow the proposed dates until early May 2013. There is also a discussion about adding M7, a Developer Preview milestone to the JDK 8 schedule. This will be the best time to encourage individual developers, open source projects, and JUGS to help test the JDK. This should help identify, prioritize and fix issues faster, and hopefully prevent a repeat of the Lucene issue, where a loop optimization bug was discovered by the Apache Lucene developers a few days before the Java 7 release.