Group content entities now also support tokens so that they may be used by modules such as Pathauto. The Group module now ships with a pre-configured Pathauto pattern for group content entities. This will not be forced upon existing websites!
If you wish to benefit from the pattern on an existing website, create a bundle and language independent Pathauto pattern for group_content and set the pattern to: group/[group_content:group:id]/[group_content:pretty-path-key]/[group_content:id]
This will make members appear at group/X/member/Y as well as the old group/X/content/Y.
Content plugin authors that have something meaningful to show at the actual GroupContent entity page may choose to set a pretty_path_key in their plugin definition to make use of the corresponding token. Plugins that don't, may omit the key and their group-to-content relationships will still show up at the default group/X/content/Y.