The "Left 4 Dead" series has been one of Valve's most successful franchises other than "Half-Life," but a third game has never been released despite numerous rumors. A new rumor from Ecumenical News suggests that the game is indeed in development and could be released by 2017.

According to the report, Valve is planning to move to a bigger office and this could signal the possibility of the company hiring more employees to start developing more games. At the moment, Valve is mostly preoccupied with the Steam digital platform and their deal with HTC to make the HTC Vive VR headset.

The lack of a dedicated development team may be why the company has not yet launched games such as "Left 4 Dead 3" and "Half-Life 3."  With an expansion on the horizon the company may now have the manpower to finish the games which have long been in development hell.

Further indication of the game was teased when Valve artist Tristan Reidford showed a file and a destination folder for what might be the tutorial for "Left 4 Dead 3." The initial image has since been taken down but it is available for fans to see on Valve Time. Comments on Valve Time point out that Reidford might simply be pranking the fans.

The post on Valve Time also reveals that the image was initially shared on June 28 but was immediately taken down and replaced with a similar image but with all references to "Left 4 Dead 3" edited out. It is possible this is Valve trying to hide the game's existence until the company is ready to unveil it and announce a probably release date.

However, given that many game developers and other companies have already released their fiscal reports, with no mention of "Left 4 Dead 3" in any document, it is possible that the game is not going to launch until late 2017 or even in early 2018.