The default plugin for local tasks will now by default populate variables in the route path using values taken from the current request (if possible).
The values are taken by from the _raw_variables in the attributes, $request->attributes->get('_raw_variables') which contain the original values parsed from the path, not the objects loaded based on them.
As a fallback, matching values from the request attributes will be used.
In the case where a path variable needs to populated based on information outside the request (e.g. the User ID of the current user), the plugin class would still need to be overridden.
See related change record: Local tasks are provided by plugins implementing LocalTaskInterface instead of type MENU_LOCAL_TASK in hook_menu()
