Heroes of the Storm "expansion" - so what does that mean, really?

One of the most anticipated battlegrounds so far, The Battlefields of Eternity, hit the live servers after a week long stint on the Public Test Realm (PTR).  On June 30, the map's release kicked off what's being touted as Heroes of the Storm's first expansion, The Eternal Conflict, with new heroes, and new skins centered around the Diablo Franchise.

This sounds absolutely epic.  However, if there's something about it that doesn't quite make sense, don't worry.  You're not alone.  What's likely bothering you is that question in the back of your mind:  How do you make an expansion for a free to play game, anyway?

The Heroes of the Storm join the Eternal Conflict in Diablo event

It's common knowledge that for a lot of people, the number seven holds special significance - from the simple concept of "lucky sevens" to the regular usage in fantasy stories as particularly magical quantity.  Whatever your thoughts on the superstition however, it looks like the sevens have struck again - or someone at Blizzard subscribes to the belief.  After seven maps centered around the new Nexus setting, Blizzard has decided the time is right to start drawing on its existing universes for battleground inspiration, starting with Diablo.  Ready to pick a side in the Eternal Conflict?    

Come into my parlor said the spider to the hero - thoughts on Tomb of the Spider Queen

As many League of Legends players will tell you, when any online game has several maps or modes available, queue times will naturally be longer or shorter as maps fall in and out of favor with the player-base.  Anyone looking for a good game on Twisted Treeline or Dominion can attest to that (self included).  Eventually, even those who like the less popular maps will give up because it simply takes too damn long to find a game.  Blizzard got around this by taking out the element of choice and making each game take place on a random battleground.  While this approach presumably allows Heroes of the Storm to have a great deal more maps and game modes than its competition, it brings its own set of limitations.