We don't have a major CS release in September, but we have pushed several patches and hotfixes. You can find the details in our patch release notes:
We'll be back in October with another major CS release of new functionality! It includes the new Data Designer (fka, Bionic Reporting), Solutions Marketplace (for importing pre-built configurations and assets), and many enhancements!
The Sandbox upgrade is on Oct. 1, and the Production upgrade is on Oct. 15. NXT customers will receive the upgrade on Oct. 5.