"Sorry I haven't been on Twitter much lately. We are in our death march push to finish game. Lots left to do. Looking forward to [multiplayer] in August," he said.
Pressed for a specific period in August, Rubin said, "Middle."
A middle-of-August reveal would match up with this year's Gamescom, which takes place in Cologne, Germany, August 21-25.
Activision has previously revealed that Call of Duty: Ghosts will feature second-screen support for the game's multiplayer component, though specifics have not been divulged.
Call of Duty: Ghosts arrives November 5 for the Xbox 360, PlayStation 3, and PC. The game is also in development for the Xbox One and PlayStation 4, though release dates have not been announced.
For more on Call of Duty: Ghosts, check out GameSpot's previous coverage.