Is Microsoft prepping for a post Windows 10 RTM Insider build?

Now that Windows 10 has shipped and is reportedly running on 50 million devices, attention will no doubt turn to the successor to Windows 10, dubbed Redstone; but before that, Threshold Wave 2 is expected to arrive by October.

We know that Windows 10 Mobile and Windows Server 2016 has already moved to the Threshold 2 (TH2) branch, and the next builds of Windows 10 will also make that jump as it prepares to enter the Insider channels for testing.