Microsoft is now testing Windows 10 build 17089 internally. The new Redstone 4 (v1803) update build 17089 (10.0.17089.1000 rs_prerelease.180129-1400) was compiled on Jan 29, 2018. Windows Insider team might roll out build 17088 this week.
Windows 10 preview build 17083 is now available for the Insiders. The latest build brings new features, bug fixes, and various other improvements. Timeline feature is also receiving several new changes in this build to put you more in control of your privacy. You can read more about this build here.
The ISO files for Windows 10 build 17083 are also now available for download. You can download it from the link below.