A thread in the New Input section of the forums has a link to a beta that it says is “based on the upcoming 2018.1 beta”.
Input System Update page-2#post-3329735
http://beta.unity3d.com/download/4f520c3a3153/public_download.html
It’s intended to test the latest attempt at a new Input system though and has no release notes so who knows what else.