There's no doubt that Overwatch has been quite successful for Blizzard, and the studio seems to have taken a liking to the first person shooter genre, if recent information that has emerged online is anything to go by.
Two new job listings reveals that they're looking for a "Lead Software Engineer, Engine" and a "Lead Software Engineer, Tools" to work on an unannounced FPS game. Could this be related to the recent cancellation of the Overwatch graphic novel? Maybe Blizzard decided they wanted to tell the story in a single player focused Overwatch game instead? The studio hasn't made many first person shooters through the years so it's interesting to see that they're working on a new one. It could be anything from a new IP, one of their popular franchises going first-person, or a new Overwatch - time will tell. What do you hope for?