From Mary Jo's piece (with my emphasis):
When will Windows 10 for Qualcomm be available? Microsoft officials are only saying in 2017. But my tipsters said the Cobalt emulation technology will be a Redstone 3 feature, which means Fall 2017. I'm assuming that means Fall 2017 for Windows 10 on Qualcomm, too.
"The concept to retail shelf timeline is normally two years," said Terry Myerson, the head of Microsoft's Windows and Devices Group, when I asked him earlier this week about timing. (It's not clear right now when the "concept" phase of this officially began.)
...Microsoft is walking the Intel-ARM tightrope, by trying to make it clear that Windows 10 on ARM is meant for a specific class of devices, namely mobile PCs of the greater than 6-inch screen variety.
Microsoft will be offering Windows 10 on Qualcomm to OEMs across a variety of categories, including 6", 10", and 14" categories, Myerson told me.
While Windows 10 Mobile remains Microsoft's version of Windows 10 for anyone interested in building a Windows 10 phone, Myerson did tell me that "we're not drawing a sharp distinction between phone and desktop" when it comes to which version of Windows 10 device maker opts to use.
That said, the aforementioned emulation layer included in Windows 10 for Qualcomm is not currently designed to work on Windows phones, Myerson said.
Initial guesses at the availability of a first party Surface phone from Microsoft had been for Spring 2017, but it looks more and more like it any possibility of such a launch will be Autumn 2017 now, with that quoted 6"-screened form factor that I went into detail on here. There's a worrying phrase above, mind you: "offering Windows 10 on Qualcomm to OEMs", implying that Microsoft is relying on third parties. However, we do have first party Surface hybrids and laptops, so why not have a flagship Surface 'phone' too?
The exact interface on a 6"-screened device with 'Redstone 3' isn't known yet. There's no reason why the existing Windows 10 Mobile tiled interface couldn't be used as a 'Start' (pun intended), so even though the OS used might be classed as 'Windows 10' (i.e. without the 'Mobile' bit) the core interface and UWP apps will be identical. So the naming thing is perhaps a bit of a red herring.
(We do know from the quote that the Cobalt x86 emulation won't be enabled on 6"-screened phones, but that's as expected - can you imagine running legacy Windows apps with interfaces designed for a 15" laptop then running at 6"? The experience would be utterly horrible.)
All of this adds up to more patience being needed for Windows fans, of course. "The concept to retail shelf timeline is normally two years" - if we take it that the concept phase started a few months ago when OEMs were shown Microsoft's plans under NDA then we could be looking at Autumn 2018 for third party 6"-screened phablets running this particular OS version. Hopefully the Microsoft first party device will split the difference and arrive in 2017, along with the finished Redstone 3....