As was expected, Microsoft today merged the Windows Insider Fast Ring, which has been testing version 19H1, with the Skip Ahead Ring, which jumped ahead to 20H1 last month, into a single 20H1 Fast Ring:
Hello Windows Insiders, today we are moving the Fast ring forward to 20H1 and merging the small group of Insiders who opted-in to Skip Ahead back into the Fast ring with the release of Windows 10 Insider Preview Build 20H1 Build 18875. That means Insiders in the Fast ring and those who opted-in to Skip Ahead will receive the same builds going forward.
This is par for the course with Insider builds, with Skip Ahead Ring testers, usually a small select group, moving ahead to the next version while Fast Ring testers finish up on the previous cycle, and then merge back together. The only twist in the plot is that we've somehow skipped over an entire version cycle (19H2) for now. Microsoft has confirmed that there will indeed be a second 2019 release, and that it will be included in Windows Insider testing at some point, but has yet to describe exactly why we've jumped so far ahead, or how running two concurrent version cycles in testing is going to work.
Anyway, If you're in either the Windows Insider Fast Ring or the Skip Ahead Ring, you can download 20H1 build 18875 today. If you have been in the Fast Ring and would prefer to continue testing 19H1, now's your last chance to move to the Release Preview or Slow Rings (Settings > Update & Security > Windows Insider Program.