Microsoft is now in the final stages of development of its upcoming Windows 10 Anniversary Update. Microsoft has been very tight lipped on when exactly we'll see the Anniversary Update launch to the public, with official comments extending no further than "sometime this Summer." But now, as Microsoft begins finalizing the Anniversary Update, "Version 1607" is official as internal Windows 10 builds are now being referenced as such. Surprise! The Anniversary Update is arriving around the anniversary of Windows 10!
Sources familiar with the matter have told me that the Windows 10 Anniversary Update (Redstone 1) is now "feature-locked", and has been for a little while now meaning work on new features has stopped and a focus on bug fixing and stabilization has begun. We may still see a few small changes and features make their way down the line before RS1 launches officially, but any major new features are now being pushed back for Redstone 2, which is scheduled to launch in the first quarter of 2017.
I've also heard that the latest internal builds of Windows 10 include more improvements to the Settings app, and all round general UI improvements and tweaks on the lead up to official release in July. This is it folks, the final descent has begun. We've got a bit over a month left of development before Microsoft signs off on a "final" build of the Anniversary Update, which will likely be flighted through Insiders first before reaching the public sometime in July.