AMD's Lisa Su let slip in April that the Windows 10 release is scheduled for late July. The Verge is now reporting that Microsoft is still on track to hit a July date, according to sources "familiar with the matter."
The Verge's sources give a little more structure to the timeline. They claim that Microsoft was originally considering announcing a July 29 launch date on April 29 at its Build conference, putting three months between the announcement and the launch. The company didn't go forward with the announcement for fear of not hitting the date.
The report says that the company is aiming to finalize the Windows 10 code by the end of June. This point would traditionally be known as "release to manufacturing" (RTM), and historically there has been a gap of several months between RTM and actual end-user availability. This time was used by OEMs to prepare new machines and get them into sales channels in time for the official launch.
That timeline is greatly condensed compared to the past, a reflection of the new approach to development and releasing that Microsoft has used with Windows 10. The Windows 10 release should be a usable operating system, but in some sense it isn't feature complete: we know that, for example, Microsoft is going to add extension support to its new Edge browser, but the initial Windows 10 release won't include that support. It will be delivered in the coming months as Microsoft continues to update the operating system as part of its new "Windows as a service" approach.
This means that the stream of preview releases will continue even after launch. The previews aren't merely a feature of the beta period; instead, Microsoft will be offering early access to Windows 10 features on an ongoing basis. The "RTM" version is a point-in-time snapshot of Windows 10's development. It should be a stable, production-ready snapshot, but it's a snapshot all the same. The process that created it will continue.
The new approach to releasing also means that users of the Insider Preview likely won't have to wait until the formal release date to get their hands on the RTM build. We'd expect that Microsoft will still have some kind of event or marketing blitz to mark the launch (and, with it, the availability of hardware with Windows 10 preinstalled), but Windows 10 should be in people's hands already.