We know that Windows 10 for PCs and tablets will be released on July 29, and Windows 10 Mobile for phones sometime after that. Now, a leak may have nailed down a timeline: the end of September.
A somewhat obtuse document obtained by Neowin puts the launch of Windows 10 Mobile "late next quarter"--or at the end of the third quarter, otherwise known as September. The source is a leaked document that lists some of the product numbers and dates for Windows 10's launch into the reseller channel.
It's also unclear whether this will be the date that Windows 10 Mobile phones begin shipping, or the date that operating system will be completed. (Users participating in the Insider program will receive the RTM build of the OS when hardware makers get it, Microsoft has said.)
That's all we know at the moment--and, as Neowin notes, it does make sense. Microsoft's Joe Belfiore said recently that the Windows 10 launch will be followed by Windows 10 Mobile, Windows 10 for the Surface Hub, Windows 10 for the Xbox, and the HoloLens edition, too. The implication is that most of the fall will be taken up by staggered Windows 10 launches for various platforms, one after the other.
Microsoft doesn't seem wholly committed to the timeline, however. Although the document refers to the end of the third quarter, Neowin's source seems to be hedging, calling October the most likely month to release the new operating system, with a possibility that it could be pulled in to September.
Why this matters: Personally, I felt like the recent Windows 10 Mobile preview build 10080 felt more like a real phone, after earlier builds really gave off the impression of a development platform. Still, the desktop team frequently releases builds that are clearly in the tweaking stage of the development process. Windows 10 Mobile is far along, but certainly not quite there yet. An additional couple of months couldn't hurt.