PowerShell Core has an RFC open to make a breaking change where modules that don't have "Core" as one of the entries in the CompatiblePSEditions field of the module manifest will fail to load (and omitting the field will cause it to default to @("Desktop")).

Part of the RFC also proposes that being on the PowerShell Core module path means the compatibility check is skipped, but since PSReadLine 2.0 already breaks compatibility with PowerShell v3/4, it could add the CompatiblePSEditions field without any harm (I think).