Check out our new page detailing the last several releases and the time they took to develop. See how we’re trending—if we’re taking more or less time to get things out of the door—and use it to predict when our next one’s due: http://lastpublishedrevision.com/
Similar to “when to buy” sites for Apple products, use this as a gauge for release frequency. We aim to provide a major release every 4-6 weeks. Keep in mind, on-premise customers can upgrade at any time, and each release is cumulative from your previous version (so if you skip a few, the next one you upgrade to will include all releases in between). Hosted customers are upgraded within 30 days of each release.