Heavenly Sword for the PS3 will definitely be a one-player game upon release. But the Ninja Theory team have not ruled out the possibility of making it multiplayer sometime in the future. Ninja Theory co-founder Tameem Antoniades told EuroGamer:
“There’s no multiplayer mode in Heavenly Sword as our focus was always to create an intense personal [...]
"Heavenly Sword - Maybe Multiplayer?" - 16.05.07