More Left 4 Dead 3 stuff in the latest Pipeline video at the 1:12 mark:
Worth noting that the L4D3 folder was last modified July 31st 2012, and the concept art she mouses over was last modified June 12th 2012.
The game must have been in development for a while.
This video is from last year.
She posted this to her blog in February 2013, and it includes the image from this video.
Also the computer says 2012 on the clock in the video