Windows 10's July 29 "launch" next week is not a typical one for Microsoft. It's just the start of a slow and staggered rollout for the company's newest operating system.

Next week marks the start of availability of Windows 10 for PCs and tablets. Later in calendar 2015, as Microsoft officials said earlier this year, Microsoft will deliver Windows 10 Mobile for ARM- and Intel-based Windows Phones and new small ARM- and Intel-based tablets. Windows 10-based Surface Hub conferencing systems, HoloLens glasses and various IoT devices will happen starting later this year and beyond.

On Microsoft's earnings call earlier this week, Microsoft CEO Satya Nadella provided a rough timeline as to what Microsoft watchers should expect over the next few months, in response to a Wall Street analyst's question about the trajectory.

Nadella said the initial Windows 10 rollout would happen in three phases. The initial upgrade phase starting July 29, which is focused on getting Windows 7 and 8 users to upgrade, plus "retail execution." Then "come the fall you will see the devices from all the OEMs going into the holiday quarter," Nadella said.

Nadella said Microsoft's OEM partners have "over 2,000 distinct devices or configurations already in testing for Windows 10 upgrades, as well as hundreds of new hardware designs." Some of these devices will be available on July 29, but the majority are likely to be coming later this year, in time for holiday 2015.

Nadella also noted that "we have a release of enterprise features ... which will ship in that (fall) timeframe and I expect piloting to start and deployments to start in the second half of the fiscal year."

"My bullishness for Windows 10 is more in the second half of the fiscal year," Nadella said, which is between January 1, 2016 and June 30, 2016.

What are these enterprise features coming this fall, which may be considered part of the Threshold 2 update?

In Microsoft's matrix comparing the features available in the different versions of Windows 10, there's a footnote acknowledging that "Enterprise Data Protection" won't be available immediately for Pro, Enterprise and/or Education editions. That functionality is coming"some time later." EDP isolates personal data from corporate data to prevent data leaks. So I bet that's one piece.

I also think the Business Store for Windows 10, a Web-based Store portal for companies distributing their own apps, might be another of those fall deliverables. And maybe those promised Universal Skype messaging, phone and video apps could be in this category, too. As Neowin noted this week, Microsoft has committed to making previews of these three apps available later this summer.

The original launch plan for Windows 10 called for Microsoft to deliver Windows 10 by fall 2015. But the Windows team decided to step up the pace and actually hit the back-to-school window with a new version of Windows for the first time in a number of years. Dell officials also acknowledged this acceleration in plans to Thurrott.com's Paul Thurrott.

Just a reminder: I've heard previously from sources that Microsoft is going to deliver a larger Windows 10 update with a number of new features this fall, most likely October. The codename for that update is Threshold 2. And after Threshold 2, we'll see next year's ongoing feature and security update parade, as well as two larger groups of new features for Windows 10. Those groups of updates are codenamed Redstone (probably 1 and 2) and most likely coming in spring/fall 2016.