I'm not one to get into rumours much as 9 times out of 10 we don't have enough of the story to make any sort of educated guess at what it actually is. This doesn't appear to be any different as it's posted on Neogaf by a guy that has some incredibly wise words to add to his discovery.

"jU$st fel acros myd esk, mbight b a thin.g"

My word, we just might have something here!

Legitimate or not, the supposed leaked PowerPoint screencap that might be from Valve shows off some interesting stuff, namely just the plantation finale of The Parish campaign in Left 4 Dead 2 re-created in what is claimed to be Source 2, Valve's upcoming game engine. The screenshot looks damn good, let's be honest. I love the little details like the faux-stone pillars splintering like wood just like they would on an actual plantation because none of the pillars were actually stone.

The PowerPoint presentation is said to be back from 2011, which would explain why the trees look a little 2009 and only makes it more plausible that this would somehow slip past people at Valve without anyone raising too much concern about it.

At the end of the day, these are just some pretty screenshots without a whole lot of proof that they're actually anything relevant. If anything they just serve to remind me that I kind of really want Left 4 Dead 3.