Well, Microsoft didn't announce the "RTM" of Windows 10
Spring Creators Update /whatever it's called today, but they did push out a new update, this one a bit unique as it's available for all Windows Insiders, whether you're on the Fast, Slow, or Release Preview Rings. Here's the news, as posted as an update to last week's announcement of the release of Windows Insider build 17133 for the Fast Ring:
UPDATE 4/10: We have released KB4100375 (OS Build 17133.73) to Windows Insiders running Build 17133 in the Fast, Slow, and Release Preview rings. This update includes the following quality improvements (no new OS features):
- Addresses a PDF security issue in Microsoft Edge.
- Addresses an issue that, in some instances, prevents Internet Explorer from identifying custom controls.
- Security updates to Internet Explorer, Microsoft Edge, Microsoft scripting engine, Windows kernel, Microsoft graphics component, Windows Server, Windows cryptography, and Windows datacenter networking.
As you can see, there's not much to the update, although it does address a security update which appears to be somewhat far-ranging. (Update): The update is promoting itself as "Windows 10 Version Next," perhaps lending credence to a move away from the "Spring Creators Update" name, although it's doubtful that this is anything but a placeholder:
Anyway, get to downloading and it shouldn't be too long before we see Windows 10 1803 finally make its way to the world at large.