Today, Microsoft released Windows 10 build 19613.1005 to the Fast ring. It's a cumulative update for the build that was released last week, so there aren't any new features. In fact, Microsoft didn't note any fixes either, only saying that this is to test the servicing pipeline for builds in the Fast ring.
The Redmond firm announced back in December that the Fast ring would no longer be tied to a specific development branch, eliminating accountability for introducing features in preview and not releasing them in production. In other words, this shouldn't be tied to this year's 20H2 or next year's 21H1. It's just an update to test servicing ï»¿on the development branch.
With that said, it's just a random cumulative update. Being that 20H1 is now in the Release Preview ring, one may try to draw the conclusion that Slow ring Insiders are going to be able to test 20H2 soon. While that may be true, today's patch is not evidence of that. 20H2 is going to be a minor update like 19H2 was, so the build will actually be more along the lines of 19042.
To install today's update, you can get it through Windows Update, or it will install automatically. If you're not on the Fast ring yet, you can enroll through the Windows Insider Program tab in Settings.