Windows Central has some background info and writes the final build will likely be distributed to Window Insiders on September 14. The public release is expected in the first half of October 2018, and will likely come with a day-one patch that fixes some small issues.
The Windows 10 October 2018 Update will launch as version 1809, and I'm hearing from my sources that Microsoft is planning to internally sign-off on this release on September 25, with plans to begin rolling it out to the public in the first half of October. Assuming all goes according to plan, Microsoft will compile the build it intends to rollout to the public on September 14, and will test that with Insiders before signing off on the 25.