The original Left 4 Dead was released back in 2008 and has since gone on to sell millions of copies. So it was no surprise when Valve announced Left 4 Dead 2, which saw a release in late 2009. The total sales for the series are well over 11 million, but we haven’t seen an inevitable third installment in the series confirmed in development. Until now, that is.Members of the Dota 2 Reddit community recently got to tour Valve’s Bellevue offices, and they were allowed to use their cameras. The results of the photo shoot were compiled into a 33 image album on imgur, and one of those images turned out to be quite revealing.The image you see below is of the Valve project change log history:Zoomed out it doesn’t look like anything special, but if you zoom in the following entry is revealed (click to see full size):That looks to be Left 4 Dead 3 using the second generation of the Source engine. Although Valve may have overlooked such an entry, it does seem to confirm what everyone expected–that Left 4 Dead 3 is a real project that we’ll hopefully get to play soon.What seems to have been overlooked, possibly because it’s not official, is the creation of the website L4D3.ru. If you visit that page you can see a Left 4 Dead 3 logo and timer, which infers something will be revealed in 15 days, so Wednesday, August 21. If that turns out to be real, we don’t have too long to wait to hear about the game officially.