It appears The Chinese Room's Everybody's Gone to the Rapture and more could be coming to Steam.
NeoGAF found other entries: Criminal Girls, Steins;Gate, Bad Rats Show, Code of Princess, and even more interesting, Final Fantasy 10/10-2 HD.
More games found digging through the files can be found through the GAF link.
SteamDB notes the recent Steam update has resulted in the package names being exposed "as a result" of not being hidden when Valve "implemented functionality to automate some frequently asked Steam support questions such as permanently hiding a game from your Steam account."
"Due to the way Steam works, we are now also able to guess some app names that were previously unknown based on what packages they are in," notes the site. "Many of these kinds of leaks turned out to be real in the past, it is important to note that third-party Steam developers can create and name their own apps/packages."
The above statement is why you may see Half-Life 3 listed in some of the files.
SteamDB also stated that many of the files outed could be older entries and no longer in development or coming to Steam - one example being Halo 3.
Anyway, have a look at everything through the links.