Late tonight, Microsoft pushed out Windows 10 build 16299.15 to the desktops of Fast Ring Windows Insiders across the world. Coming about seven days after build 16299 was released, this build does not bring any new features or fixes. It does, however, release about two weeks until Microsoft plans to roll out the Windows 10 Fall Creators update to the mainstream public (October 17th.) And, although not confirmed by Microsoft, this latest build might also likely be the final RTM build for the upcoming Fall Windows 10 featured update.
— Dona Sarkar (@donasarkar) October 3, 2017
To add to the speculation of this being RTM of the Windows 10 Fall Creators Update, Microsoft revealed that the company is testing out servicing this build via Windows Update. Just as it is currently done on retail versions of the Windows 10 OS, this likely means that there won't be significant increases in build numbers soon, and only minor cumulative updates.
UPDATE 10/2: We have released Windows 10 Insider Preview Build 16299.15 to Windows Insiders in the Fast ring. As we prepare to release the Windows 10 Fall Creators Update to the world on October 17th, we will now start testing out servicing this build with the Cumulative Updates via Windows Update.
Again, this is only speculation of this being an RTM build. Dona Sarkar has said before that Windows Insiders would clearly know when an RTM build has arrived. Since she's been quiet about it thus far, and there is not much new to say about this build, we're only contemplating on the RTM status.
Anyway, as detailed by Brandon LeBlac, this release is essentially the same build released last week, except that is has been changed to 16299.15, with no watermark on the desktop. So don't expect any big changes after downloading. Do keep in mind, though, that things are now becoming much more stable! So, whenever this build releases to your ring, you might be wanting to use it as a path out of the Insider Program.