Legacy of the Void will be released on 10 November, just two months from now, and will conclude the StarCraft II story. More to the point, with Blizzard's interest in single-player games apparently waning and no more StarCraft material planned, it is possible that this game will conclude the entire StarCraft saga, at least for many years to come.
StarCraft II: Wings of Liberty, focusing on the Terrans, was released in 2010 and was a solid game, if a bit uninspired compared to the excellent original StarCraft (1998) and its expansion Brood War. The first expansion, Heart of the Swarm, centred on the Zerg species and was released in 2013. It was a stronger game, although fans were incredulous at Blizzard taking almost three years to release the game. Legacy of the Void now arrives a further two and a half years down the line, still using the same engine and many of the same assets as the original game released in 2010. It is safe to be said that Blizzard's release schedule here has been pretty disappointing, even by their slow standards.
Hopefully Legacy of the Void will bring an element of closure to the StarCraft storyline, because if not it will certainly be a long, long time before we see any continuation to the story.