The build number that Microsoft is expected to roll out to mainstream users beginning April 11 is 15063 (the build that shall not be called "RTM," but which really is RTM, as in "release to mainstream"), along with a number of subsequent fixes and updates which will be installed along with the RTM code.
Those who really don't want to wait can jump the gun and proactively get Creators Update now. I've asked when Creators Update will be available to MSDN subscribers and Volume License customers. Microsoft officials said they'd have more to say on that closer to April 11.
Update (March 30): Microsoft officials said that April 5 will be the day when savvy users who want to update to Windows 10 Creators proactively can go grab it using the Microsoft Update Assistant tool. From today's blog post:
"For the those of you who are eager to get the Creators Update right away, you will be able to initiate the update manually, starting on April 5th, via Update Assistant. This option is intended for advanced users on devices running a licensed version of Windows 10."
Microsoft has been testing the Creators Update -- the successor to the Windows 10 Anniversary Update -- for the last several months inside the company and with Windows Insider testers. The Creators Update includes a handful of new consumer-focused features, include a new Game Mode, Beam game streaming, Windows Mixed Reality support, and new ebook and tab-management capabilities in the Edge browser. Microsoft will include a new 3D Paint application with this release, but still continue to make regular 2D Paint available alongside that release.
Microsoft demonstrated in late October 2016 a companion 3D mobile application that would allow users to capture 3D images on their phones and subsequently edit and even 3D-print them. Microsoft is not commenting on when that phone app will be available. (I asked again recently.)
Windows 10 Pro, Enterprise, and Education customers will be able to defer feature updates (such as Creators Update, Redstone 3, etc.) for up to 365 days and "quality" updates (bundled security updates and fixes) for up to 30 days. Home users still will not have a new option to defer or pause either type of update, thus continuing to serve as yet another wave of testers for Windows 10.
The Creators Update will be a free update to those already running Windows 10. Microsoft has not yet said how much it will charge for the Creators Update if purchased as a standalone product. There will be Windows 10 Home, Pro, Enterprise, and Education versions of the Creators Update for PCs and tablets. The Windows 10 Mobile version of Creators Update will come to phones "over time," a spokesperson said. Creators Update also is coming to Xbox and the Surface Hub.
Microsoft officials still are not commenting in any way on the Cloud version of the Creators Update, which is a version of the product that can only run Windows Store apps and will be upgradeable to Windows 10 Pro.
Surface Book with Performance base is available for pre-order starting today in Austria, China, Denmark, Finland, France, Germany, Hong Kong, Japan, Netherlands, Norway, Sweden, Switzerland, and the UK and will be available for purchase on April 20. Surface Studio and Surface Dial are available for pre-order starting today in Australia, Canada, and New Zealand and will be available for purchase starting April 20.
Microsoft still has yet to announce timing or details about its expected Spring 2017 hardware launch. I've heard there won't be a Surface Book 2 unveiling at this event, but we may see an incrementally improved Surface Pro 5 and possibly some other mystery hardware.
On to Redstone 3, which Microsoft is expected to release in the Fall of 2017.
Android users in Australia finally get their hands on Cortana: