Today, we got confirmation that build 16299 is the RTM (final) version of Windows 10 Fall Creators Update. The build 16299 has been released by Microsoft to Slow Ring Insiders and is now available on the Fast ring. This could be proof that Windows 10 build 16299 is the RTM build.
The official announcement about Windows 10 Creators Update should happen in October 2017, that is, this month. Yesterday, a new cumulative update KB4046355 for Windows 10 Build 16299 increased the OS version to 16299.15.
Now we can expect Windows 10 build 16299 on the Release Preview Ring and then in the production branch. Also, it is quite possible the OS could get more cumulative updates in order to fix minor issues left in the build.