Yep! Try building a new version of the package using the Yak CLI in a recent Rhino WIP; the minimum Rhino version will be inferred from the RHP and the package will be specific to Rhino 6.
It might also be a good idea to yank the current version to avoid confusion.
Right now, if the package is tagged for Rhino 6 then it will still show up in the package manager in Rhino 7 WIP, but the installation will fail with a “not compatible” error message. In future, I’d like to communicate the compatibility of packages better in the UI. I’d also like to allow, for example, packages that contain Rhino 6 plug-ins to install for Rhino 7 because in many cases we’re able to avoid forcing plug-in developers to recompile their plug-ins by limiting breaking changes to the APIs – it would be good to not force developers to repackage their plug-ins either!