In PowerShell 5, the distribution model for ISE is in the process of changing. Until version 5, ISE was released as a part of the Windows Management Framework (WMF). New features were introduced with each version of WMF, but the time between the versions was long.
ISE Preview may be installed from the PowerShell gallery using the following command:
Install-Module -Name PowerShellISE-Preview
Once installed, the update-module command may be used to bring ISE up to par with the published version.
ISE Preview can coexist with the version of ISE installed by the WMF package.