In a tweet, Tero Alhonen announced he was able to modify and use the Windows Media Creation Tool to install Windows 10 RS4 build 17134.1. Alhonen's supposed breakthrough was based off a tweet by WalkingCat (@h0x0d,) who linked to a Redstone 4 XML file.
— Tero Alhonen (@teroalhonen) April 26, 2018
(Update:) To run this "hack" you'll need to do some workarounds and edit some files in the existing Windows 10 installer, using WalkingCat's XML tool above, and then the Media Creation Tool which is available here for download. The process is a bit technical and involves adapting the .xml to work with Media Creation Tool, so it might be out of reach for some general users.
There is a rumor that Microsoft intends to unleash Windows 10 RS4 at Build 2018 on May 9, 2018. If you don't want to wait that long for the release, you can grab up the update on any Windows 10 PC right now with this installer hack. Of course, you also can use the Windows Insider ISO files for a cleaner install of Redstone 4 then and then head to settings and "opt out" of the program, which is much safer and viable option for general users.