If you use one of the available tools that help organize groups of Agile stories, it may support the concept of bundling stories up into a theme. You might simply refer to the theme by what it really is: your next release, the feature, or the stories relevant to a particular type of user.
It seems that Jira is at odds with this approach since it does not really have themes and Epics are made to be closed. Seems more useful to me to use epics as themes so you can drive towards a release.
