A possible Left 4 Dead 3 document has been spotted on NeoGaf and looks to feature a map redone in Source 2.0.
The title of the post named “l4d3? (Source 2 reveal)” shows the plantation finale from the Left 4 Dead 2 campaign, Swamp Fever. The picture claims that the map from Left 4 Dead 2 was rebuilt in Source 2.0 and has an “increased level of detail,” the power point reads. The power point also looks to have other screen shots from Left 4 Dead 2 in the original Source engine and then the same screen shot redone in Source 2.0.
Source 2.0 is the engine that is currently being developed at Valve and was confirmed in late 2012. After numerous rumors and leaks it is possible that Left 4 Dead 3 may be the debut game for Source 2.0.
It should also be noted that Left 4 Dead 3 is not noted in the document, so, this could very well be a tech demo for the second Source engine, rather than something related to the next installment in the Left 4 Dead series.