As a test, I just downloaded the newest version of Windows 10 using the Media Creation Tool. Although I don't really want to run the upgrade install at this time, the build number 10.0.15063 of the downloaded ISO DOES seem to coincide with the above articles about the Creators Update being available using the Update Assistant and in my opinion, possibly the Media Creation Tool.
https://betanews.com/2017/03/24/windows-10-creators-update-rtm-final-build/
Still, it's very possible there will be small additions to the 15063 build in the next few days. A few tweaks could be added to the build making it number 15063.xxx, etc. I'm just passing along the info I'm seeing at this point as I don't want to install on any mission-critical machines for a while..
Hope this helps.
Grif
Or, for those that just can't wait, (most don't advise jumping off the cliff), the Creators Update can be downloaded and installed today.
The first official method for downloading the Windows 10 Creators Update outside of the Windows Insider program starts on Wednesday, April 5. That's when anyone on build 1607 (the Anniversary Update) can download and run the Windows 10 Update Assistant to move to the latest and greatest.
http://www.pcworld.com/article/3187408/windows/you-can-download-the-creators-update-april-5-for-a-head-start-on-windows-10.html
Some more information is also in the links below:
https://support.microsoft.com/en-us/help/4014184/windows-10-creators-update-here
http://www.computerworld.com/article/3187586/microsoft-windows/review-windows-10-creators-update-is-here-and-worth-the-download-with-video.html
As mentioned above, and because these large releases have had their issues in the past, it's not generally recommended to take the leap ahead of the standard release date. As for me, I'm waiting till April 11th to download the ISO and install the upgrade after a fair amount of time has passed.
Hope this helps....
Grif

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