The release schedule for Ubuntu 13.10 has now been firmed up on the Ubuntu Wiki.
Key details for this next Ubuntu Linux release include:
Feature Freeze - 22 August
Ubuntu Beta Release - 26 September
Release Candidate - 10 October
Ubuntu 13.10 Release - 17 October
Continuing in the Ubuntu 13.04 trend, Ubuntu officially will have less development releases (though its derivatives can opt-in to do alphas and another beta) with Canonical continuing to push more on the daily usability of Ubuntu development images.