The listing includes the further codename “Marmalade Content”, which ties in with the “Project Marmalade” codename for Sackboy: A Big Adventure that was found in the huge Nvidia database leak back in September.
A listing for Sackboy: A Big Adventure was briefly found on SteamDB, before the details were completely locked from Steam.
The listing, codenamed “Steel PC”, has one key giveaway that reveals that it is indeed Sackboy.
Moreover, a number of games in the list have since been officially announced, most notably God of War’s PC port.