Blizzard is already working on "another project" for Overwatch
However, the current game will continue to expand.
At Blizzard's last financial meeting, President J. Allen Brack spoke briefly about the present and future of Overwatch: "It is an outstanding franchise for Blizzard, and we will continue to dedicate resources and attention to it so that the community and the series grow with time". The work plan not only involves improving the video game that we know so far.
Brack explains that the team will continue to add "new heroes, new maps and new experiences" during the new fiscal year: "they will work on the existing game [...] and focus on the another job they have in hand". This new project is particularly interesting for two reasons: one, that it is used immediately after talking about the" existing game "so it does not seem to be a simple free addition; and two, that it does not illustrate if we are talking about a sequel, spin-off, campaign mode, movie or anything else.
That said, a couple of days ago IGN published an interview with Michael Chu, chief scriptwriter and central axis of the Overwatch narrative, where it was mentioned that the game's story has a relatively similar structure to that of the Marvel Cinematic Universe. Most of the events, comics and cinematics presented so far are focused on the past to illustrate the background of the characters and corporations that shape the universe, but all this forms a "first phase" that culminates in the cinematic "The call" ( the first of the whole game). What happens next It wouldn't be strange to imagine that the new Overwatch project picks up on that same point.