Yesterday at the Surface Event, Microsoft confirmed that build 17763 is the final RTM build for Windows 10 version 1809 aka October Update. The build is already available for both Fast and Slow Ring users.
This means that users now have the opportunity to leave Windows Insider program if they’re not comfortable testing the early builds of 19H1. Usually leaving Insider program means users will have to reinstall the public version of Windows 10 but right now the public version is the same as the Insider version which happens twice a year. Microsoft might still rollout some final patches to the build before finalizing it and moving to 19H1 branch. When this happens, you will have to wait till spring of 2019 to go back to public release without the clean install.
We don’t know when Microsoft will push the first 19H1 build to Fast Ring so if you’re uncomfortable testing it then make sure you leave the program as soon as possible. You can do so by going to Settings>Update and Security>Windows Insider Program and clicking “Stop Insider Preview Builds”. However, this doesn’t mean you can’t join back but the first few builds of 19H1 will be rough and it’s not recommended to install them on your daily driver. That said, you can come back to Fast or Slow Ring later on when the builds have been stabilized and there are no major bugs or issues.