While Windows Insiders have been testing out Windows 10 20H1 since February, Xbox Insiders have been testing out 19H2, which is right around the corner now. That means that it's time for Skip Ahead Insiders to start testing out 20H1, and the first build is available now.
The build is number 18975.1004, so it's similar to what's currently in the Fast ring for Windows Insiders. Unfortunately, there are no new features just yet. Microsoft says that the feature set is the same as 19H2 for now.
This will likely stay like that for a while too. Xbox is different from Windows in that it gets monthly-ish feature updates, rather than semi-annual feature updates. That means that whatever you see in 20H1 will likely be bundled into whatever monthly update is coming out, and the real 20H1 features won't show up until later. Of course, one of those features could be the redesigned dashboard.
20H1 is still a ways off, due to be released next spring. The Xbox One version is being called version 2004, which means that it's due to RTM in April, 2020.