It’s also possible that the game could see a jump to a different time period, but it hasn’t been specified if that will be in the future or in the past. It would be a strange development in any case though, as the first two games shared the same timeline.
In fact, they even shared some events, and Valve did a great job tying them together once they released “Left 4 Dead 2”. While it will still be possible to do something like that even if “Left 4 Dead 3” takes place in a different time period, it will be a more challenging task.
Other rumors talk about a larger number of players, and an expanded multiplayer mode. Some fans have been skeptical at the former suggestion, claiming that four was the ideal number of survivors for a tense, yet exciting experience.
Plus, the name of the game will make little sense if there aren’t 4 survivors anymore, so we definitely don’t expect Valve to change this aspect. There are plenty of things that can be changed in the original formula while still keeping the game fun, but the number of survivors seems to be something that most fans agree should be kept intact.
As for Valve themselves, needless to say there has been absolutely no statement from the studio regarding their current projects on the actual game development side, and we don’t expect that to change soon. They seem more focused on “Counter-Strike: Global Offensive” and “Dota 2” at the moment, as they have been for a while.