Looks like the Devs are taking a hiatus from L4D and returning to TF2.

"We've been pretty quiet lately, but thankfully, that's about to end. In the next few days we'll have an update out that has a couple of new features for the Engineer and Spy, and a variety of other smaller fixes.

The next class pack will be the Scout. One of the main goals we're focusing on for him has been to provide tools that make him useful in maps like Dustbowl & Goldrush. If you have any ideas for what you think would work well, post them over on the Team Fortress 2 Forum and we'll take a look."

Source [2]