Yesterday, Microsoft released build 14393 for Windows 10 Preview and Windows 10 Mobile Preview. As the new build addresses some system issues and contains no new features, it looks like just a regular Windows 10 Preview build at first blush. But, it can easily be more than that.
As ZDNet's Mary Jo Foley points out, there are a few facts indicating that Windows 10 Preview build 14393 could be the Anniversary Update RTM build. Foley also said her sources told her that Microsoft plans to stop releasing Preview builds on July 20th (today as of the time of this writing), which fits well with the release date of build 14393. Reportedly, Microsoft wants to sign off on an Insider preview test build in order to better prepare for the Anniversary Update release.
Another thing that could indicate that build 14393 is indeed the RTM build is that Microsoft promised to release a few updates for a few known issues in the build. So, it won't take a whole new build to fix those issues, but instead, Microsoft will eventually release a patch through Windows Update.
On the other hand, Microsoft showed no signs of an RTM release recently as the head of Microsoft's Insider Program, Dona Sarkar, announced build 14393 just like all builds before it. But that's not surprising since Microsoft stopped using the term RTM because Windows 10 is presented as a continually updated service.
However, a lot of people are still using the RTM (release to manufacturing) or the RTW (release to web) terms to refer to a major update, like the November Update or the Anniversary Update.
It remains to be seen if build 14393 will indeed be 'the one,' but we'll find that out soon enough with the Anniversary Update scheduled to be released August 2nd. So, if Microsoft doesn't release a new build in the next seven to 10 days, expect build 14393 to be released to regular users as the Anniversary Update for Windows 10.