Based on the release of the betas this year, and compared to the release of the betas last year, Computer World thinks that this could indicate a release between the 9-15th of October. “If Apple follows a schedule similar to last year’s — when it released the El Capitan upgrade on September 30 — Sierra’s slower beta cadence signals a launch the week of October 9-15.”
While we suppose that is a possibility, so far Apple’s releases of its OS updates have typically been in October to begin with. For example OS X Mavericks and Yosemite were released in October, while El Capitan was launched at the end of September, so it woudn’t be surprising if Sierra was indeed released in October, but we guess narrowing it down to the 9-15th of October might be more specific.
In any case we’ll keep an eye out for Sierra’s release, but if you are looking forward to getting your hands on the update, you can always check out the public beta if you’re too impatient to wait for the official release.