I think you're going to get a huge mix of fabrics, but no, not the least popular. One month, you might get a theme - plaids or paisleys or Autumn, the next month, you might get Kansas Troubles, Fig Tree, etc. I really don't know how the Moda Medley of the Month specifically works - that's just an idea.
I get the Civil War Medley of the Month and I'm happy with it - many manufacturers, but a narrower focus.