Earlier today, Microsoft released Windows 10 Insider Preview build 15042 to the Fast ring, bringing a few minor new features and a number of fixes. There is something else that's definitely worth noting though: both the Insider Preview watermark and the expiration date are gone in this build.
This shows that the Creators Update is getting close to completion. It's slated for an April release, but it has a version number of 1703, so the don't-call-it-an-RTM build will likely show up next month.
If you're not familiar with the watermark and expiration date, you can check out the screenshot below which is from build 15031.
But to be clear, 15042 is most certainly not RTM. There are still a number of known issues that need to be fixed, and if you check the version number in the build, it still says 1607, which was the Anniversary Update. It does, however, seem like a likely candidate for the Slow ring, now that the updating issues have been fixed.
Indeed, this just takes us one more step closer to the Creators Update. This has historically been normal procedure when leading up to the final build of a feature update. When that arrives, there will likely be one or two more cumulative updates on top of it, it will be offered to the Release Preview ring, and then to the public.
Thanks to Steve Truman for the tip!