Unfortunately there is not a RSS feed for featured content in any version of Jive. However there is a News feature, I know it's not exactly what you are looking for but in Jive 8 and Cloud instances there is a News feature which allows Community Managers to create streams for users in your community: What Are News Streams?
If you are interested in having the option to have a RSS feed for featured content within a space, I would recommend submitting an idea here Ideas for Jive. This will allow other users to vote up the idea and help give the idea visibility for our products team.
Hope this helps.