At BlizzCon today, Blizzard's Mike Morhaime announced StarCraft 2: Nova Covert Ops. Nova Covert Ops is a 3 mission pack coming to StarCraft II in the Spring of 2016.
https://www.youtube.com/watch?v=NImK4R5wEfg
Blizzard fans will recognize Nova Terra in the trailer as a playable character in Heroes of the Storm and as the onetime protagonist of the cancelled Starcraft: Ghost, though Nova Covert Ops will not be bringing anything from Ghost to the table.
Talking about Nova Covert Ops in an interview with Polygon, Starcraft II's executive producer Chris Sigaty stated
"We’re focusing on a story that’s a little more intimate, a little darker in tone, "We’ve been so focused on the galactic conflict [in StarCraft] and the galactic story. We’d like to explore something a little bit closer to home."
We don't know much about Nova Covert Ops yet beyond the stylish cinematic trailer released by Blizzard and embedded above. However, Blizzard has stated that additional mission packs will follow the release of Legacy of the Void on November 10th 2015, so we do know there's going to be more StarCraft coming.