That's called Reddit! Rather than basing anything on popularity, wouldn't it be much cooler to have a button called "Random Unfollowed" which just grabbed any post by any user you're not following and brought you to its comment page? That'd be a great way to discover guaranteed new stuff without having to worry if the "Most Popular" page is going to become the Front Page of Hubski. Maybe you could set a # of followers range in controls for your "Random Unfollowed" button, so you'd only get posts by people who you don't follow but someone does.
If you go to your controls page you can set the option 'external posts' to some or many to get some posts in your feed from people you don't follow. Those posts will turn up pale blue in your feed so you can visually identify them as well.