Starcraft II is still a powerhouse of a competitive game, with 1.6 million dollar prize pools up for grabs in the 2015 competition and with over 200,000 players still active.  No denying, this is still one of the most played PC games to date.
Their latest expansion to the franchise, Legacy of the Void, not only marks an end to the Starcraft II story but is looking to provide a strong mix to the gameplay including the addition of new units:
Protoss Units - Adept and Disrupter
Terran Units - Cyclone and One TBD
Zerg Units - Lurker and Ravager
You can read all about the improvements and expectations on their official blog post.  Subtle changes will improve changing resources near the base, starting worker count, improved target acquisition ranges, etc. Players will be able to test out the new tweaks with the closed beta, which begins on March 31st.
Starcraft II's last expansion, Heart of the Swarm, sold 1.1 million copies on its first day alone and was generally well received by fans and critics alike. 
 - Battle.net - Legacy of the Void Beta Preview - http://us.battle.net/sc2/en/blog/18291111/legacy-of-the-void-beta-preview-3-18-2015
 - SC2Ranks - http://www.sc2ranks.com/stats/league
 - Polygon - Starcraft 2: Heart of the Swarm sells 1.1 million copies in two days - http://www.polygon.com/2013/3/21/4133306/starcraft-2-heart-of-the-swarm-sells-1-1-million-copies-in-two-days