Last slide says a little bit on that (once again, if this is real): Someone else on the ValveTime comments shared another photo from one of the other slides. Updated OP with it. He also stated these are from 2011 (rumor of course).
I am just curious how someone even gets a leak like this. I can understand concept art but screenshots of files and folders seems so random. And a single screenshot of a PowerPoint slide, even weirder. If this is even real is it possibly a staged/planned leak?